My working dog has started to typewrite on the arm, and has since develop dirty biting techniques because of previous poorly trained agitators. Any suggestions on how to re-train her to bite the sleeve correctly and hold?

I'd go back to basics and play with this dog yourself. Start with a tug and then move up to bite pillow, then sleeve. Here are the videos that I'd suggest:

The Power of Playing Tug with your Dog
Teaching Protection Skills Without a Decoy

You don't mention her age, but you may also be interested in Foundation of Puppy Bite Work. I've used this for older dogs (18 months) as well as little pups.

I hope this helps.

Cindy Rhodes