Here is a link to a few recipes from Garry Howard's site. Garry is a champion competition BBQ'er and Chris Schlesinger is a reknowned BBQ chef.
I would go with the first rub recipe and, if cooking in the oven, the first sauce recipe listed in the link. Garry's BBQ Recipes
There are millions of variations of BBQ rub and sauce recipes all over the internet, but these work, especially if you want a smoky flavor without a smoker.
If you DO want to add natural smoke to your meat, I think the best way for you to handle these is to smoke the butts, in batches, probably, on your grill, at a low temp for say 3 hours per batch. As each batch is done, throw it in a 250-275 oven until they are done and you can twist out the bone with your hand. If you do this, look up a BBQ sauce recipe that DOESN'T use liquid smoke.
Note: if you have to speed up the cooking due to time constraints, wrap each butt in heavy duty aluminum foil for the last couple of hours of cooking.