I had to adjust my setup so I could prime these 4 pieces. I put them each on a box and used that to move it in and out of there. I'd spray one, then switch it with another, and again, until I got them all, then wait a few minutes before hitting them from another angle.
It took just over an hour but they're coated! I see a few rough spots, holes, and scratches. I'll wet sand to 400 tomorrow and putty fill again.
After that, I took some putty to the barrel. I don't know what happened with this piece, but I had to fill A LOT!! I took a new approach, based on my extensive experience of puttying 5 pieces lol. I'd just rub the putty around with my Play-doh knife to spread it across the imperfections but not leave too much to sand later.