I have 3 latching relays installed in the little module that I made. I am currently running two relays from those, 1 to a light bar and the other to spot lights mounted in the grill. I have one spare latch for the next accessory I find. Haha. Thinking compressor or something along those lines.
I used 400 grit sand paper, I am impatient though. You can use 800 grit and possibly save the white under, but it takes a lot longer than I want to spend on it. Maybe a 600 grit compromise would be decent. 400 works for sure. I wrapped the sand paper around the tip of a screw driver for better accuracy.