Michael, finding a ten pound butt shouldn't be a problem, especially if you find somewhere that carries the Excel pork butts. I buy butts from a small local store here in Lebanon anyway, since the Sam's pork prices aren't really a deal anymore. No idea why they've become so proud of their pork. I catch the sales and buy all pork for much cheaper than Sam's.
Regarding rubs and smoke, etc...I prefer a spicier rub for butts than ribs. However, if I was to pick one commercial rub for both, it would be Plowboy's Yardbird, which has no msg, if that's an issue. It's a really good KC type rub for pork or chicken. You can find it at Bass Pro Shop if you don't want to order any.
I usually make my own rub, and you might do some searches here on the site to find out what's popular here...You'll probably find that Kevin Kruger's recipe comes up a lot, also the BRITU back rib recipe, (although I'd dismiss the "method" and just use the rub). As for butt rubs, I think that a lot of folks like the "butt rub for Jane", if I remember correctly. Chris Lilly is a fantastic pitmaster and has some great recipes out there, although I've found that both of his pork butt injections were a little heavy on the salt. (Never tried a cola injection, though.) One other that comes to mind is Harry Soo's (Slap Yo Daddy BBQ) recipes off his site. I don't keep up with comp. bbq, but I know that he's won a lot on the wsm and has been on bbq pitmasters and such on tv.
Even if you don't ever try any of the recipes, be sure you check out Chris Allingham's wsm tips and cook documentation, especially since you are gonna use Kingsford. (Keep in mind that he's found, like most of us have, that flipping, rotating, mopping or spritzing isn't necessary for good bbq, though.)
As to smoke, you might find that it's almost impossible to oversmoke a pork butt on the wsm. Ribs and chicken are a different matter all together, though. Just sayin that you want to use plenty of wood for the shoulder butt, especially if using such a mild smoke wood. One thing that I've learned about the wsm is that more moisture in the wood is better than well-seasoned...ESPECIALLY for pork butts and briskets. It's a whole different ballgame from smoking in a stickburner where the wood is actually burning, not just slowly smoldering.
Main thing though is.... use enough time and heat to get it all done in time. Foil is your friend, both before and after the meat is done, if necessary. Regarding temps, although I prefer 235* for butts and 275* for back ribs, I don't have a ATC (automatic temp controller), and besides, there's no reason to be anal about temps since I find that 225-275* is just fine for all bbq cuts. I highly recommend hanging a therm in the vent instead of going by the factory gauge.
Good luck with it!
