I think compelling scene aspects is the easy part of the question.
Like, if one character is shooting and has the aspect "wild uncontrollable bursts" I can definitely compel him to have his shots go all over the place, and then I can turn to the wizard and say "there are shots all over the place, give me a dodge roll at a difficulty of 4." I don't have t compel the wizard at all in that case. I can alternatively compel the shooter and place a scene aspect "errant gunfire!" Now, as long as the shooting is still going on, I can compel folks. What I don't like is short cutting the fiction to just say "hey wizard. That guy over there, he's got an aspect for shooting wildly, here's a FP because of his aspect which I haven't really established as relevant yet, this is especially so, if the shooter is a PC, but even with an NPC, I'd follow a show don't tell philosophy and establish the wild gunfire in the fiction, then have its impact felt. I think the experience is actually enhanced by doing it that way.
More on this later.