I built a really crude wooden frame with some chicken wire attached. I would drag out my empty trash cans, put the frame over it, and then lay down the parts. Mind you, I live in a warm climate where this worked just fine 12 months of the year. At the end of the build, my trash cans were all fully primed.
Another tip: mix up just a bit more primer than you think you'll need, and when you fill up the spray gun, leave a little bit out. You'll find after spraying, you might just need that little bit extra to get it all covered. Using the two part epoxy primer and having to wait 30 minutes for it to induce correctly was a pain at times.