^^ If you're a hairy SOB, start w/ the electric clippers and use a new razor (or as many new razors as it takes) w/ shaving cream to get rid of the rest. Start several weeks out from the show so you have some time to deal w/ the ingrown hairs and stuff. That's not something you want to start putting layers of competition tan over.
The optimal (and most convenient) approach for competition is to hire the advertised competition spray tanning service. It tends to be a bit pricey, but usually top quality & done in 2 visits - if they are good (e.g. Jan Tana does an amazing job!) - 30 min for all your layers & time to dry to just past tacky w/ their fans, sleep covered up, then a touch up the morning of (usually at the venue).
The reason I bring this up is that you don't have to start doing your tanning layers until the night before the show, which also means you are only going 1 night w/o shaving to reduce the stubble & growth you end up w/ on stage. (This means once you get your tan on, you can't shave again w/o fucking up the tan.) If you have already been shaving, then the afternoon before your tanning session, do the electric clippers for the worst of it, and have someone help you w/ a new razor & shaving cream. Then hair should be the least of your worries on stage.