DB, if you have chunks use them instead of the pellets...otherwise you are going to be adding them many times during the cook...and that means opening the cooker a lot. Never a good idea to open it any more then you have too. Plus your looking at a 16hr cook or so with an 8lb butt.
I use pellets for grilling more then smoking...especially if you don't have a pellet burning cooker.
If you are going to use them no matter what, I would fill a foil pack with a lot of them and throw them in when you add your coals to get started...If you need to re-fill, and it sounds like you will have to at least once or twice, then make a few other pouches to tranny in an out during the cook.