Prepare the body by sanding off mold lines and making needed modifications with putty.
Wash in warm water with laundry soap. dry. let sit so all the water drys.
Rig the body on your spraying rig.
use your plastic-compatible primer (dont use testors, or we will beat you up
) and put it in a sink of hot water for a few mins.
take can out of water, dry. shake vigorously for 1-2 minutes, yes that long. it's worth it.
get your model on the rig, check for dust. use a tack cloth to take off any lint or dirt.
hold the can of primer about 8-10 inches away from the model and spray evenly. go very light on the first coat. wait about 5-10 min. a little more on the 2nd coat, wait 5-10 min, and get coverage on the 3rd. make sure you get FULL(outside, inside, cracks) coverage of the model if you are using automotive lacquer (duplicolor).
let the primered body sit in a dust-free, temperature regulated place (tupperware, anyone?) for about a week so the primer can harden.
if you want, you can sand down the primer with some 1000+ grit sandpaper to smooth it out for painting. I'd rather just sand and polish after the paint has been applied.