No new progress. I was out of town on vacation so lost a couple of weekends on the truck.
I am NOT the best to give advice on anything to do with bodywork and paint, but I'll try to answer your questions, even though those answers may be embarrassing to me
I'm hoping that these products are actually more forgiving than the impression you get from reading a lot of threads on this site.
The gun I'm using is a Central Pneumatic Professional that my dad gave me. I'd guess this is Harbor Freight. Comes with 2 tips, 1.4 and 1.8. I thought I was using the 1.8 for the epoxy primer, but your questions got me to look at it and I've been using the 1.4 tip - go figure
Seems to be working fine, but I think I'll change to the 1.8 tip for future primer spraying.
As far as sanding before primer, most of mine has been sprayed over bare metal which got that way with 80-grit. If I'm spraying over Rage filler, I've been sanding the filler down to 220 grit before spraying the epoxy. If I'm respraying an area that has already been primered, I'm scuffing it up with the purple 3M scotch pads. I don't honestly know whether or not that is going to provide enough "texture" for the new coat of epoxy to stick best, but seems fine so far.
You are supposed to be using a wax and grease remover compatible with your paint "system" prior to spraying the primer. I've been using mineral spirits - bad me! Actually, in most areas all I've done is blow the dust off with the compressor. At this point, the epoxy seems to have gone on fine - hope my laziness doesn't come back to bite me.
I'm drying my air with a setup I purchased from Eastwood. I do make sure I drain the water from these as well as the compressor before spraying.
One thing I've learned is that this is not nearly as daunting as you'd think if you do too much reading & thinking. Once you've done it a time or two it becomes pretty routine. Do make sure you know how to disassemble your gun and have the laquer thinner, brushes, toothpicks, etc. all laid out ready to clean the gun when you are done spraying. I watched several you-tube videos on cleaning the guns before doing it the first time myself.