From everything I've read, you want the spray on the exterior of the intercooler, either from the top or bottom ,when using a top mount intercooler(TMIC).
adding water to the inside of the intercooler sounds more like water injection, not intercooler spray. Go to www.i-club.com and do a search...
IIRC, mothballs are Paradichlorbenzene. Their effects on engines I do not know. If any of your engine's internals are made of wool though, I think you'll have no problems from moths. =)
