I wouldn't recommend using that high of a dosage Yve. I would go with Kolleens advice of "Mix 2 mls of Ivomectin with 1 litre of distilled water and use as a cage spray." if you were determined to use Ivomectin. I don't think that bathing the snake in the solution would benefit you at all. I also feel that there is a chance of consumption of the solution there as well and there is no need to do it. Spray IMO is the best way when using this treatment.
Nix works better IMO as well. It's less costly and wont go stail like an Ivomectin solution. (2 weeks) You can keep it for future use when an animal is in quarantine new animals.