And for problem areas that even liners cannot protect, use Leukotape.

This stuff goes on and stays on for a week, even if you bathe. You can use it like moleskin by cutting a hole, or using it plain. For example, if you have a tendency for repeat problems with a heel or a toe, cover the area with Leukotape before you go, add the aforementioned poly liners and Merino, the Bobís your uncle.