Your dog needs a bath.  If you are to do this yourself, here are some things you will need to know.

 It is important to Dilute the shampoo.  In a 16oz bottle pour about an inch of shampoo in and fill the bottle up with warm water.  Shake it up to mix.  I dilute the shampoo because it is easier to rinse completely off than concentrated shampoo.

 Dilute the Conditioner too.  In a 16oz bottle pour about 1/2 inch of conditioner, fill the bottle up with warm water and shake well to mix.

 Cotton Balls.  It is very important that you do not get any water in the dog’s ears.  This will cause ear infections.  Put the cotton or half a cotton ball in the ear before you bath the dog.  I bathe the head last because once you get the head wet the dog will shake.

 Ear Powder is good to put in the ears after the bath, just in case you accidently got water in the ear, even if you don’t think you did it is better to be safe than sorry later.  Be sure to fill the ear canal full and massage the ear before you let the dog shake.  You may want to do this outside.

 You will need a slicker brush for long coated breeds.  I usually brush out a dog (not matted) while he has the conditioner on him in the tub.  After I am done brushing, I rinse him entirely from head to tail and under arms and belly and tail.  You can squeeze the water out and look, if it runs clear, the soap or conditioner is out of the coat. Use the Shampoo, rinse then use the conditioner and brush.

 Towel dry as much water out of the coat as you can.  You can let him air dry if it is a nice day.

 I like to use Blow Dryer, a human dryer, set on the warm setting, not hot.  I brush as I blow dry  until the dog is dry to the skin making sure there are no mats on long haired dogs.

 If your dog is too matted, he will need a haircut first.

 Hint, stand to the front or rear of the dog when he shakes, this way you can minimize the unintended shower you may get.