
Different terrier breed, but may be interesting...
The same thing happened to my wire fox terrier. The groomer noticed that stripping was becoming harder each time, and by the time Bracken was three the hair appeared to be welded in place. Bracken is 6 now and her coat still appears to be welded in place. Fussy visitors who don't want dog hair on them and try to keep away from her, are challenged to have her on their lap for the duration of their visit and see if they can find a single hair afterwards! It would be funny except the coat care is awful.
I've tried Coat Kings, undercoat rakes, thinning scissors etc etc, and in the end have had to resort to a clipper and scissors. Her coat is fluffy, woolly, thick and mats in seconds, and she looks like an old english sheepdog puppy (and has been mistaken for same by some people!) For everyday brushing (and it has to be every day) I use a terrier palm pad and a Les Poochs Pro Brush (the firm one). I clip her myself now every couple of months, quite inexpertly, but she ends up looking pretty much like a wire fox terrier for a few weeks at least. I don't clip her legs, but scissor the furnishings, and use scissors to get out any matted bits I have failed to remove when brushing. Beard and part of face also gets scissored. Luckily the breed club have a DVD which shows how to clip a wire fox terrier.
Breed club members said that I had been unlucky for the coat to turn so bad after spaying, but some seemed to think that had I left spaying until she was older the coat change might not have been so bad. This suggestion comes from those with older, spayed ex-breeding bitches. Bit late for either of us now though!
Not much help for you, but lots of sympathy!
Claire and Bracken the (not so wire) fox terrier.