I've seen guys post about using various types of tape for gap sealing, but don't really remember the brand names as I don't do it that way.

Depending on the coloring, I use either clear UltraCote (they call it transparent rather than clear) or I color match with UltraCote. I've also seen guys post about only doing one side, but I think that'll lead to accumulation of debris especially if you use tape, so I do both sides of the surface.

JMHO, YMMV....