I use Cowboy Rub from The Spice Hunter quite a lot. It is in most grocery stores around me, with the rest of the spices, and is salt free. As for the shrimp, you might find that smoking the shrimp with shells on and the sausages separately works better for you, then peel the shrimp and assemble your skewers. Not as much fun as pulling them from the smoker ready to go, but the shells help buffer the smoke and protect the shrimp from drying out. I agree with the others that you might try a different, milder wood than cherry. Alder is traditional with fish on the west coast, or maple is pretty mild as well. Good luck, and tell us how you make out.