I agree with trying some water, usually you will be able to drown some of them out, but he may not like that too much. Perhaps some mite spray will help?

I know that in the shelters we use a mild saturation of dish soap on really tough cases of ticks and fleas. I've seen it done with snakes before; Maybe a quick rinse with that will help.

Just make sure you are careful and to keep the snake away from your other animals (which I'm sure you know already), and I wish you the best of support, hope and luck