Very old cat and grooming issues

[Seaoftroubles]

My lovely old girl is 20 now and although she is contented and well in herself she's stopped grooming herself and her coat ( shorthaired) has become very matted and scurfy. She has always been feisty and although she loves being stroked she will not tolerate me grooming her and does not hesitate to bite and/or scratch.And at her age I don't want to distress her any more than I have to.
I think it is probably because she finds it uncomfortable as she is so boney now -but it could just be that she doesn't see why she should put up with it! So, any advice on a gentle but effective grooming tool that will do the job-and that she might tolerate?

I ended up using a furminator v v gently with my 19 year old girl. Little and often. Sometimes alternating a stroke then a gentle stroke over with a brush can help. And catnip!
Thought of asking the vet about any supplements?

Thanks Wolfie will have a look at the furminator..am about to order her a heat pad from Amazon so will add that too.I am loathe to take her to the vet as it would be stressful for her, but might see if I can get a telephone appointment. She is pretty thin but she is happy and very loved and spoiled. We are always tempting her with different 'treats' and nibbles.She rules the house tbh!

YY to heat pad. It did wonders for our old girl.
Grooming mitt?
Could she have arthritis? Our old girl ended up on tramadol for that.
Ruling the house? So she should!

We have one of those Zoomgroom brushes. It's rubber/silicone (shaped like a cat for some reason) so gentle on the body if she's on the bony side.

Seniorboy can no longer truly groom himself - apart from his 'personal' grooming which luckily he can still manage happily. (He's of an age with your cat and also has very severe arthritis.)

I use a brush comb - I think they're called 'styling brushes' - and only go for his flanks, throat and chest. I avoid his belly because that appears to be very sensitive but doing the rest on a daily basis (so not very long each day) seems to work fine. I also nip the tips from his claws because he hasn't any longer got the balance or muscle power to really go at his front ones or the teeth to gnaw his back ones. He gets by on that anyway and seems to enjoy it these days. (The grooming, anyway - the claw attention I think is more just toleration.)

Thanks everyone, Heat pad and Grooming mitt ordered for starters..will see if the mitt makes an impression, and if not will try the furminator or the brush comb. Better get some cat nip too!