How would everyone recommend going about dipping my whole 04 sportwagon? I was planning on picking up a few bottles of the 11oz spray cans today to do my roof and emblems. Say in a couple weeks I plan to plastidip my whole car... Should I buy by the gallon (more specifically how many gallons?) and will it blend in with my already dipped roof? I'm thinking flat black, if that makes any difference at all.