When treating the tank, or whatever he is in don't put his water dish back with him for 24 hours. He should be fine.
I recently had a mite scare, and I got recommondations from 2 close friends to use Equate, that you can pick up at Walmart to treat the cage itself. I used Reptile Relief to to treat the snake outside of the tub, which i put it on my hands and rubbed the snake down with it.
Worked perfectly. Most people are afriad to use Equate, considering it hasn't been proven to not harm snakes like PAM has. I have had no issues using it, as of others who use it on a regular basis.
Hope all is well, and that you fix your problem!