What kind of paint are you painting the bottom of your car? Base/clear or single stage. I plan on doing the body base/clear. I've heard different ideas.
The guy painting the outside of mine told me to do it base/clear. I wanted to do it single. He said something about if it wasn't taped 100% perfectly and he got some spray on it. It could cause issues. Not sure how true that is but I wasn't going to risk it for a couple hundred dollars.
While the car was on the rotisserie my undercarriage was sprayed the proper shade of gray using enamel paint. The body colour overspray on the undercarriage was then sprayed using acrylic enamel. The undercarriage area was then completely masked off prior to spraying the body with base coat/clear coat.
My orange car was correctly done in primer with single stage overspray. My Green car was done in base/clear and although incorrect it makes it easy to wipe off and keep clean.