Double coats and mats

I have an 11 y/o Norwegian Forest cat (Spaz) who does not tolerate brushing.

Some back story..
When she was a kitten, she loved to be brushed several times a day.
I kept an herbal flea repellent around the apartment for use with my dog, as the cat was highly allergic to it.
My then boyfriend, thinking it was a good idea, and not knowing better, applied the oil to the brush.
The result was an extremely sick and uncomfortable cat.

I still try every day to brush her, and retrain her to enjoy it, and I'll keep trying until she crosses the bridge.

It was not really much of a problem, as she is a great self groomer, and would tolerate the twice yearly baths quite well.

When she hit 9 though, she started having problems shedding her undercoat, resulting in terribly bad mats which have to be shaved.

Is there anything out there that can help in the removal of such extreme mats, that won't bother her tender skin?

I really hate resorting to shaving her beautiful tortie coat.

You may have to keep her shaved if she just won't tolerate brushing. One of my persian's is the same. She has a kidney disease and they tend to have super sensitive skin (from what I've learned). There is not much else you can do if the just don't tolerate brushing. My cat gets down right violent about it. There is such a thing as a mat blade. They have them at petco. But if she won't tolerate brushing, she probably isn't going to tolerate the mat blade.

She'll sit still and let me gently pull apart maybe two or three small ones, but it's not the small ones that distress me.

She doesn't really even like the shaving, but I only work on her for as long as she starys calm, she too, gets violent, my poor fiance' got a nasty bite from her while getting shaved the last time, and he wasn't even involved, just closer to her teeth.

It just eats me up though, in the winter, when she has her full coat and ruff, she has the most beautiful tortoise shell brindling.

Ashley has the same issues with matting, but I have noticed it more so since she has gained some weight (maybe she can't groom as well..or reach, rather?).

I HATE these things and like your cat, she HATES brushing (I use more of a slicker type of brush because regular bristles like soft bristles don't cut it). It pulls and who can blame her?

I do, though, use those small scissors that have the curved blades (what do you call those things that cut???? LOL!) to get them out. If I am really careful, Ashie is fine with it and doesn't know what I am doing.

And....you know what? I need to post my own question on this topic....