Who is administering the BBQ contest? If it's a biggie like KCBS, you'll want to check their rules pretty close. I know that most require the BBQ to be done on site during the event.

I've never done a competition but my brother in law Frank used to be an a BBQ team that did comps regularly. He's won some ribbons. I'm sure he'd be happy to give you some pointers on what judges are looking for.