Exactly this. And pre-treat paper towels and allow them to dry so that you can replace soiled ones with treated ones when your snake makes a mess.
ETA: you can use the reptile spray every 3 days. I spray a white paper towel and wipe the snake, which gives me an idea of how quickly the infestation is being killed off since the mites show up on the paper towel. I also keep treating for 30 days after I found a mite, since eggs can lay dormant for that long.