Personally, I have done lots of ribs with and without foil and the ones with are more moist due to the fact that they are cooking in their own juices for a few hours. I try and keep the smoker closed as much as possible during the cooking time to maintain the temp as best as possible. The only drawback I could see by only spraying them every hour is that they might tend to dry out but, since I wrap them in foil towards the end they stay nice and moist and fall right off the bone. All the meats I smoke, except fish, get a rub or marinade the day before. I feel that is the best amount of time to absorb the flavors of your rub or marinade. Everyone does things different and thats the beauty in BBQ.
Weber One Touch Silver
Oklahoma Joe's 20" Barrel Smoker aka "Betty"
Keep it Smokey