I just finished stripping my galvanized gutters and am ready to repaint. The gutters have a little rust on the inside, but are perfect on the outside. What should I use as a primer? In particular, should I use a different primer on the inside (because of the rust) than on the outside? I'd appreciate any recommendations people might have -- the more specific the better (down to brand names if you have had a good experience). Having just spent 60 hours pn a ladder stripping these things I want the paint to last!