Chris,
You may want to take a look at Brodac's line of dopes, primers and fillers. I have been using them for a few years now and can vouch that they are a far cry better than Sig and Aerogloss. It is a Mill Spected product that has not changed since the thirties. Flows nice from an inexpensive touch-up gun. Most of the time it is sandable in thirty minuts and with a clear coat, glosses out like a mirror. One layer of mediun and a top layer of lite silkspan and it is tougher than plastic covering and repairs without a visable trace. Check them out at: http://www.brodak.com/
Good luck,
"Geppetto"