I've just been using a simple circuit tester in the past (nitrous system) to find a power source, but I'd like to find the ignition switch wires/fuse if possible to make it simple. Any help? Otherwise I'll just start tapping into fuse wires until all is peachy.

If it doesn't draw too much amperage, you'll find ignition-switched circuits in the fusebox below the dash (left of the steering column; there'* a release trigger you can squeeze to swivel it downwards for better access). You can tap into a red wire where it emerges from behind the fuse panel for a neat piggyback attachment. (i.e. Make sure you're tapping into an _outbound_ wire on the protected side of the fuse. Pull the fuse, then test your chosen wire to be sure it'* dead when the fuse is removed.)

Nitrous is tapped into "PWR WDO SUNRF 30A CB"....safe to tap 2 gauges into that? Or should I leave one device per fuse?

Well, first of all, that "CB" on the end designates a circuit breaker rather than a fuse, which might be a better idea anyway since it will reset itself if you accidentally overload it, and temporary loss of power windows isn't the sort of problem that will land you in the ditch if it happens unexpectedly at 60 mph.

You might try that circuit; sure. You should try to get some idea of what the amperage load of the new stuff is going to be, though; you don't want to pop the breaker if you're trying to run all the accessories on that circuit at once.