You can't use epoxy with microballons with fiberglass tape. The Microballoons will keep the epoxy from soaking into the fiberglass.

You could use resin with microballoons to fill dents and dings with, but it's going to be heavy. There are other fillers available that are much lighter.

Using 5 minute epoxy you're going to find that you won't have enough working time to mix the balloons into the epoxy and then apply it to your work area. Use 30-minute (or longer) epoxy.

A quick note about microballoons, you can substitute corn starch for name brand microballoons and get the same results. This helps a lot for those of us without a LHS nearby.

Ken