Well, of course it works - anyting that will flash-off in the pan will work, as long as it also flashes through the vent hole.
; 3F, 2F, single F will all work, but they aren't as fast as 4F. If they were, 4F would be on the market. 4F is faster in all locks. As well, it's coating doesn't seem to be as thick as the other powders, and this also improves ignition speed.
; This has come up before, and 3F(or 2F) can be slightly ground, with a pestle and mortor, to a finer granulation and will work just as well or perhaps better then 4F, depending on your skill at grinding it. Small quantities, and be careful. Some locks don't like 3F for priming and will rarely fire with 2F. Pistol locks, which spark less than rifle locks, sometimes have trouble without 4F.
: Will 2 or 3F work - yes, of course they will. Are they as good as 4F? - No, they aren't, but they will work, just as the space-saver spare tires, "work". They aren't as good, but will get the job done.