Begin with a long line parted down the spine, from the nose to the tail, and work a 1-2 inch area along each side of the part the whole length of the dog. Make a new part, 1-2 inches up from the original part and about 4-6 inches wide.  Put your hand behind the new section and begin to brush. First use a bristle brush.  If it will not go into the coat, graduate to the next brush in line, which should be a large pin brush.  If this too encounters thick spots and will not easily penetrate the coat reach for the long narrow pin brush, which allows you to attack smaller areas.  If this is still a problem reach for the "ever gentle" slicker and if that won't do it, use the ultimate ripper and go for the Universal slicker.  If this will not undo the area, you are left with evaluating the whole dog.  Is this a small area that is alone in its condition or is it indicative of the whole dog. If it is the whole dog, please, put down all your tools, go get the clippers and clip your dog down.  You can use a #4 blade if all is pretty loose but you will need a #10 blade if the mats are at the skin level.

There is another choice. If the dog has been out in the weather, the mats have been wetted, are tight to the point of not being able to get a comb into them, or lie close to the skin, you might consider this.  If the dog can be dried out in a warm place, and is otherwise in clean condition, you can put off grooming for 2-4 weeks.  Keeping the dog dry, often no more damage will be done.   In a 4-week period, the mats will have grown up off the skin level by about 1 inch and you will be able to split or separate the mats and save some coat.  Or clip the coat using a thicker blade (4 is thicker than 10) thus leaving a fuzz behind.  If the dog is dirty, really completely matted from total neglect or has sores or external parasites, do not even consider this and go ahead and clip this dog down and give it a bath.

Now that the dog has relaxed as I tested the condition of the coat, I move back to the head (unless you have had to shave the dog) and do the area from the "part", up over the top including the ear as far as you can comfortably reach.  It is at this point that you clean the uppermost ear.  Pluck any necessary hairs out of the ear canal, I save the part of the ear cleaning which calls for the use of a liquid cleaner until I am ready to turn the dog over. That way, the liquid left after the cleaning, can drain out onto a towel when I turn the dog over.   Now check the eye and scale the uppermost teeth. 

Using the tools in the order mentioned above, finish the entire upper side of the dog as far across the dog as you can comfortably reach.  Part an area about 1 - 2 inches up and carefully brush the hair sideways and then down, being careful not to hold on to the hair from above and so back comb or tease the coat instead of brushing it out straight.  If the soft brush will not go through the coat, pick up the section and brush it against your hand. In this way you can evaluate the area and if necessary graduate to the harshest tool you need to "clear" the area.  Remember that if you are grooming to keep a full coat that you are only straightening and pulling the undercoat upward through the guard coat, not pulling it out by the roots. 

If you are show grooming do not put your thumb on the back of the brush and use it as a comb or you will remove more coat than you desire.   Your brush should be grasped loosely and not forced down through the coat.   Use caution when using a slicker brush.  If you repeatedly scrape the skin you risk introducing the normally present staph germs into the scratches which can lead to large infected areas.  The brushing action should be a lift and pull not a push and scrape thus the reason for not putting the thumb on the back of the brush.  By turning the dog (if the table is big enough), moving your chair or turning the table, move around the dog, grooming as you go.

When it is time to start the legs, have the legs toward you, and start with the pad area.  Trim all the hair out from between the pads and clip the nails.  If you are using a grinder it might be best to get help until you are confident in using one.  Wait until you have the dog dry before standing the dog up, and using a grooming loop or assistant to hold the dog, do the nails with a grinder.  If you are comfortable using clippers, go ahead and clip out the hair from between the pads.  I also clip or scissor 1/2 inch behind the largest pad.  Feet are usually the part that most of the dogs do not like, and as soon as the feet are taken care of they relax again, knowing the rest is not going to be so unpleasant for them.  

Start with a comb and carefully comb all the toes and in between the toes in the webbed pocket.  Switch to the brushes in the order above and begin by brushing all the hair against the grain up the leg, using a bristle or pin brush, leaving it all pointing as much upward as it will do.  Then continue the 1-2 inch parts around the leg as you did the body of the coat.  Do the inside of the leg on the bottom when you do the top of the upper leg.  Do not rush your job and you will both enjoy it better.  I use a comb in the arm pits and in the groin areas.   The less undercoat left there to mat the better.  Use a comb on the edges of the ears, the lips and chin areas.  Clip a half circle area in front of the sheath.   (Do not remove the tassel on the end of the sheath as this aids in directing the flow of urine away from the legs and chest.)

If I am grooming at a Dog Show, I will often reverse the direction of my line brushing to leave the coat going up on the sides, forward on the back, and up on the legs and head.  If you do the show side first and leave the coat in it's UP direction, when you turn the dog over it will "iron" the hair into place for you.  If you wish to remove coat, reverse the order of grooming tool usage.  If you hold a molting comb by the toothed area as you would a pencil you can work on a mat in a piecemeal method.  Hold the mat tightly with the fingers of your left hand and insert the end tooth of the comb in the middle of the outside edge.  Pull toward you in a picking motion.  Do not insert your comb and pull for all you are worth.  This is not a fishing trip.  Remember what you are doing. 

A mat is made up of tangled hair and is much like a cord your three year old has tied up for you - knots on knots on knots and all intertangled!  What you are trying to do is straighten out the knotted area.   You should not try to pull the whole thing out by the roots. In a normal coat the undercoat strands occupy the spaces between the guard coat shafts and you are attempting to untangle the guard coat and straighten out the undercoat.  A matted coat does not insulate the dog very well from heat or cold and not at all from rain.  With a pet that you want to keep looking like a full-coated OES you must keep the undercoat manageable.  Either treat the coat as a show coat or remove the amount of undercoat necessary for you to manage the coat. 

You can keep a long coat manageable by learning to groom with a comb and universal slicker.  The biggest caution I have for anyone is to remember what is under the coat.  The skin of your dog is the only barrier between nasty germs and your dog's immune system.  You can cause serious injury by grooming too roughly.  You might be wise to clip your dog on a 3 times a year schedule.  With only 4 months in between clips you will not have a coat longer than 4 inches at any time and I personally think that OES in their "pajamas" look absolutely adorable.