there are several products that work well, PL1 is a good one. its a polyurethane based sealant. sand or scuff up any painted surface to enhance adhesion. good luck
Roger that. Great Stuff will eat metal. Fine for indoor woodwork but lousy for use on a skoolie. And for sealing any seams...use "Seam Sealer". There are several brands that are used for OEM manufacturing. They are all urethane based and available though most any auto body repair supply houses. They remain flexible and are paintable.