Best way to shoot an explosion/burst test

What is the best way to an explosion or an effect that has burst spawning?

I’m trying to shoot an explosion test and I’m trying to figure out how best to record it using FRAPs. I’ve tried playing the Emitter Duration and Emitter Loops, but it’s been hard to get the emitters in sync as the timing gets offset over time. I’m also wondering if there is a hotkey to restart the level while in play mode?