chips in gelcoat

[tsubaki]

There are several tricks, depending where the damage is, how severe, etc.
I would suggest getting a fair amount more than you need in order to play with it first.
Depending on temperature and humidity, it will set up different.
For flat horizontal surfaces, it's easy, just mix and squeegee or razor blade it into place.
Vertical and overhead surfaces needs to be applied while still tacky but not well into curing. It's usually needed to keep wiping the surface till it sets up in about the area you want.
Applying a couple of coats instead of doing it all at once is easier on overhead stuff, sand or ruff up the area's between coats.
For real hard to work locations lightly wiping with a cloth dampened with lacquer thinner will smooth the surface, make drying time a little faster and reduce sanding.
Play with a little bit of it first, you'll get the idea.

[Destroyer]

PC-11 (If you're not familiar with it think JB-Weld clone) makes a marine version epoxy paste in white. No sag, no drip, even sets up under water. Sets in 1/2 hour. Certainly not for large areas, but for screw holes, cracks and small nicks and chips it's perfect. Mix equal parts, force into hole and spread over the top...Wet your finger with spit and smooth the surface... done!