An expert doberman owner and breeder gave me this advice and I follow this exactly and it's work perfect for me , so I am passing it on to you.
these are her dogs http://www.geocities.com/shalmarchesters/dobe2.html
FIRST:
I do not use any dog shampoos on them at all.. I feel that dog shampoos are the worst.. toomuch perfume, to many dyes, etc. and a big fat waste of money. I use Pantene Pro v vitamin shampoo..have for years and it make the coats luxurious. I also use a product on the dilutes called "Eqyss Rehydrater" (you can find it at petsmart). It is a horse product (safest in the world to use on dogs.. more ph) it is cruelty free and smells wonderful and just keeps the coats "fed" and in great shape...
I do not use cloth collars either.. they get dirty, full of bacteria and can cause eruptions on the neck.. rolled leather collars , light, with a small role are better.. and make sure the metal doesnt hit the skin. no flea collars either.. if you do have cloth collars, you should wash it a couple times a week..best way is to tie it up in a pillow case and toss it in the washer.
I bathe every other weekend.. in tepid water, in the tub.. in between are wipe downs with the eqyss and the aloe baby wipes. I never towel rub either, because I have a fawn.. we blot only...and crate til dry. (so they cant rub on the ground, the rug, etc and load the clean coat up with debris) clean collar goes on after the bath. keeps the neck zits away...
SECOND:
(try changing food)
I feed nutro natural choice lamb and rice, small bites. I think it might be the food.