Moist & juicy? Alot of people overlook these important things.

DO NOT USE A MEAT FORK ON YOUR ROAST. It only serves to create drain holes. It's really simple to understand but most will put it on the grate with a meat fork and poke it to turn it and check it = drain holes.

Keep water in a steamer tray. Not a cup or little miniature pie tin, the bigger surface area the more moisture (steam) will be created. Keep the roasts covered with a complete canopy of heavy duty foil so that the steam will be totally enveloping the roast.

I've seen guys sear the roast before smoking to seal it also and it seems to work pretty good.

But when I do pork just for BBQ sandwiches I haven't found anything that beats the crock pot. I do a couple med roasts in apple juice til fork tender. Then I pull them out and flake them, dump back in crock and bath in BBQ sauce. Serve on big old rolls (buns? I can't stand buns!)

Seems like pork roast is always on sale over here at the grocery - so when we do a party thing there's a good chance it's pork sandwiches!
I do the regular anda little different batch for those looking for some zip. I add chopped white onions and chopped jalepenos.