You can put a quick disconnect right off the compressor outlet. Yeah, yeah... oil mist, bla bla bla... I've been using mine very regularly for a little over a year and the separator is still dry. Yes, there's oil in the compressor crank case, and yes, the compressor is untouched as it came out of the 1980 VW Quantum save for an oil change. However, outlet temps get hot so use 2-3' of copper pipe between the compressor and the QD to be sure.
If you do this, DO NOT start the compressor without it being connected to a tire! I did this once and it blew my hose right to s***. And speaking of hose- get this:
Air Hose, 16' Coil That's the only place I could find with an air chuck that screwed on to the valve stem; those clip on ones suck. Do your knees a favor and get it. And since it screws on, put a tee in on the hose side of the QD with a valve stem nipple so you don't have to unscrew the hose from the tire whenever you want to check your tire pressure as you air up- just shut the compressor off and hit the nipple with your gauge.
Speaking of gauges, get a $5 digital gauge from any auto parts store. I've compared several to a $150 liquid filled Motion Pro gauge, and they're dead nuts accurate.
At idle, the compressor will fill a 35" tire in about a minute. It's fast. In fact, it's so fast, you should seriously consider plumbing in QD's at both ends and then having tees off those with two of the above linked hoses so you can connect to all four tires at once and fill them up. I have this setup and it does my 33's in under five minutes, including setup and break down. It's fast. A bonus is that I have a tee with the valve stem nipple on one set and can check the pressure of all four tires at the same time. I added a dump valve and can air down all four at the same time.
For the electrical, you can just mount a switch somewhere that toggles +12V to the wire coming off the clutch. No need for a relay unless you have one laying around and want to use it.