Hey, just thought I'd chip in my two cents. GW and Vallejo Game are both good choices, as is Army Painter, though GW and Vallejo Game have a much larger range. I like GW a bit more as it seems to have more pigment that the Vallejo (which can be a little transparent sometimes). Its really personal preference.
Rule #1 for me has always been to thin you paint. I've only ever used tap water, but we have good water here so ymmv. It should be thin enough that it spreads easily but not so thin that it beads up. Its roughly 3-4 parts paint to 1 part water. Likely it will take 2 coats to cover but it will go on smoother and more importantly won't obscure any detail (and the detail on these models is pretty delicate).
For brushes, I find as long as it can hold a point when loaded it doesn't really matter what its made out of. Also, don't overload your brush with paint or you'll lose control of it. Load your brush with paint then pull it across the pallette to get rid of the excess. For pallettes, a tile is a great idea. I've used a wet pallette from time to time and they are great, you just have to keep an eye on it as sometimes the pallette paper can get waterlogged and you get little particles of paper in the paint which sucks.
I hadn't thought of spray priming on the sprue, thats actually a pretty good idea! I normally use brush on primer as I have more control over where it goes (again, don't want to obscure all those fine details).
Additives like flow improver and retarder are really only something I'd recommend for advanced level stuff. Also if you are a brush licker like me, flow improver is a bad idea as its toxic.