You can talk to GP reps until you're blue in the face. After some bad deals with Tower and Great Planes I found the best way to results is to call Hobbico since they are the parent company. Get someone in management in either sales or cutomer relations and yu're off to the races. A quick search of Hobbico phone numbers got me this 217-359-1430.

As for telling good from bad MC, a friend of mine showed me how to tell as soon as you get a roll. Just look at the backing. it should be smooth with a few lifts here and there. No tiny bubbles (gives you the grainy look) and no big or large quantity of places where the backing is lifting off the covering.