You might consider taking her to a groomer and have them shave those parts back there. That way there won't be anything for the 'residue' to stick to. Otherwise, there is always the old "put the cat in a sleeve of an old sweatshirt" tactic. I think SAS was the one that I first head this from for pilling purposes. The only thing is you'd have to cover her head instead of her body and legs, and you'd have to make sure she could get air while you're doing your thing.

Tubby every now and then has 'residue' but I mostly try and brush that part just because he doesn't let me do it enough to get it done good, and even though he's a short hair cat, he gets lumpy back there sometimes and needs to be brushed. This new shedding comb thing is slowly doing the trick though, and getting all that excess hair out of the way, which should help in the 'residue' dept. too.

Good luck, and I assume you've got her on some sort of "lite" or low calorie food? T & P had been on Science Diet Feline Maintenance Lite for years before I switched them to the Senior formula. Kept Tubby's weight in check for all those years, so it's just a suggestion.