Heating will accelerate the cure. If the piece is small enough to fit into the oven, then putting it in there with the temp. set as low as you can go will work. For larger pieces, we built a "hot box" with wooden sides and a transparent top and set it outside on the blacktop. Temps inside easily reached 140-150 F and that cured the epoxy in no time.

Doing that should help your issue. I've thought about the "brush on harder" approach when I've done that before, but I was always worried about making a bad situation worse, so I never tried it...

Bob