I just made a repair to the outside seam strip on a fiberglass kayak. I used West system G-flex epoxy and added gelcoat coloring agent to make it black. Worked great and it was easy to sand. Just follow the directions. VF
G-flex
I have had good luck so far using G-flex for repairs. On fiberglass or synthetic cloth conventional 2 part epoxy will work fine. The G-flex mix ratio is not as critical, however, and since it mixes 1:1 by volume, very small batches can be mixed by eye, which is convenient for small repairs.