I have done harbor freight red but it has been several years since I bought powder so it may have changed.
my process is as cast , I put a handful or two of bullets in a Rubbermaid 4 quart food container with about a 1/2 inch of the black air soft BBs and a tablespoon of HF red vigorously shake up and down with lid on and sealed
then with a nitrile glove on one hand I dip the thumb , index and middle finger in the powder to coat the glove then pick up the bullets and set them on the base on my parchment paper lined tray
bake in a preheated convection oven I have a little counter top type 10 minutes at 400 that seems to get me decent adhesion
to test you take a coated bullet place it on the anvil of you vice and smack it with about a 2 pound hammer , it flattens and if the coating stays on you are good
my biggest expense is that the food containers seem to crack after a few months , I place tape over the crack to make a few more then I have to retire the container
the reason this works is that 2 dis similar plastics create a static charge and that causes the powder to cling to the bullets
I didn't invent this I got it from cast boolits gunloads
I do recall them being specific that they tried different HF powders and red was one of the only ones that got good coverage
they found other better powders
also that some guys had good success with placing bullets on their nose and using the ion powder coat guns they "sprayed" them on a foil lined baking sheet then baked them it may have been non stick foil I don't recall if they had to transfer them or not.
