So how did you find out he has mites- are you seeing many? Make sure he has a water bowl (now!) that's big enough for him to soak in, but don't put soap in that- you don't want him drinking water with even a bit of soap in (it will upset his tummy!). Many snakes with mites will automatically soak for relief. Poor little guy! (Ivermectin is used various ways- injectable etc) I wouldn't worry about "stressing him out now" (ahead of tomorrow) by giving a more effective soak because the more mites he has, that's worse than any soak. Just do it- he's too little & he's probably had them for quite a while now- they're hard to see, & always more plentiful than you realize. Please don't under-estimate mites.