if the epoxy resin directions said "add x amount drops hardener to polyester resin" then it is not epoxy resin.
Fast cure epoxy is just as good as slow in strength. Only need to worry about blush in cheaper brands like US composites, West systems and MAS have little blush comparatively. Just one more step. IF your working in the summer, rule of thumb is never buy fast. I always use medium or more often slow because the pot life of fast in a butter can is about 10 minutes even if that, I like an hour a whole lot better, 2 hours even more.