I usually buy 500ml of a colour to do a body , and usually have about 200ml left when finished. I don't measure very accurately, and I mix about 1 paint to 2 thinners. I use a small suction touch up gun , I guess it holds about 200ml and that is enough to get a coat and a bit ( I do extra coats on the edges).Primer I do a pass around the edges, then a complete coat. Wait till that flash dries, then do it again. Wait a few hours, light sand , do the same, wait till next day, sand. Colour coats the same, usually wait a few days before doing the clear, then leave the clear for a week or so before sanding and polishing.