Oil and the like don't do well on bullets when powder coating, it sticks to the oil but when baked, slips off.
I cast, let em cool, push through a Lee 'push' sizing die, shake in powder, bake, let em cool, push though the sizing die the second time, load.
Do I need to size before coating? No. But that is my habit. I seldom cast and coat on the same day (same week) but have a lot of time sitting around with little to do and the first sizing operation gives me something to do. I seldom have any empty brass that is not spoken for in some special project. It just gets loaded up.
As to the initial question.
Harbor Freight Red tends to go on a little thicker for me. How much? Don't know, they get sized anyway.
PBTP powders have covered well on a one coat process. Any time I tried a second coat, it was a 'too' thick failure. All I want is for the polyester to cover the bearing surface and butt of my bullets. I've moved to a 'Clear' polyester powder. I don't have to be concerned with thin spots in the pigments in the coating. (OK, I do slip a little color in from time to time but just a hint,
neon pink and neon yellow.)
I only do 'shak-en-bake' coating. Can't speak for the much purdier spray on coating style.
Load with care and enjoy,
OSOK