I know I'm not 4FordFamily (and he's way better at this than I am) but until he gets here . . .
The only way I know of to quarantine a cleanup-crew would be to keep them in a fallow (no fish) tank for 76 days, allowing any encysted ich time to hatch out and die of starvation. TTM can work well with wrasses, but make sure your tanks are well covered! I tried it with a ten-gallon on the kitchen counter, and had a young exquisite wrasse jump through the holes in the egg-crate top ... and straight into a sink full of dirty dishes and hot, soapy water.
Now I use chelated copper, such as "Copper Safe", and an API test kit, and have been successful with several wrasses. Also, be aware that Tank Transfer Method, while it works very well against ich, works against ich _only_, and does nothing for velvet.
My $0.02.
~Bruce