Cimorene

Aaagh, in sympathy. It sounds like far too much trouble for nearly anything except, well, keeping most of your clothes instead of losing them.

In case it becomes relevant, dry cleaning (if Finnish cleaners are anything like U.S. cleaners) is safe and useful for most purposes, especially killing moth eggs, but it is expensive. If you already have the sauna, it sounds like a good option.

Second the recommendation for cedar blocks or balls as ongoing preventatives, especially in closed drawers or boxes -- always assuming no one in the house is allergic to or repulsed by cedar.