J-Rod
is Blowin Smoke!
All great advice thus far. I'll only add that there's no need to inject a butt as they got enough natural food lube already built in, and watch the wind on your cooker. If it gets windy, make a makeshift wind block with plywood or cardboard or whatever and that'll greatly help keep your temps stable and not allow wind to rob you of heat. Cook the butt till bone wiggles loose and you can stick a temp probe in it like a knife in warm butter. Have fun!