You might also check Bob Thompson's thread about painting his Airstream in which he also discusses his varying successes with Parrbond and other sealants. He by far recommended one from Home Depot, I believe, and by the time he had completed his project, he had had LOTS of experience!
1995 Airstream Classic Limited 30' ~ Gypsy
1978 Argosy Minuet, 6.0~Minnie/GPZWGN
Chev Silverado 2500HD Duramax/Allison, 4X4, Crew Cab
WBCCI #5013 AIR #2908
Go, Mizzou...Tigers on the prowl!