I've had a Masterbuilt for a couple of years (actually 2 Masterbuilts). I've had my best results with smoking heavy for about 2 hours and then wrapping in foil and finishing in the oven at 250-275 for about another 2 hours. In th smoker, I set the temp on about 225 to start and gradually increase the temp a little at a time. With a Masterbuilt, the smoking only occurs when the burner is heating. To keep the burner heating, I gradually add a few degrees to the temp to kick the burner on. You probably shouldn't end up over 250-265. You could do the whole thing on the Masterbuilt, but I figure if I'm not smoking, I'd rather use an efficient oven that will last much longer than the smoker When the meat pulls back from the ribs about a 1/4 to 1/2 inch, they should be ready to pull. Some people finish on a grill for a few minutes, and then sauce them.
As for rubs, there are thousands of recipes on the net. Usually just something with papiricka, garlic & onion powder, chili powder, cumin, and a little brown sugar. I put a little bit of crushed reds and some black pepper in as well. I found that smoking more than 2 hours, the ribs get too smokey. Hope this helps.