[SkunkBoat]

for small stuff get a box of MarineTex two part epoxy filler.
Overfill slightly and sand smooth when it hardens.

I just did a couple stress cracks. ground them out a little and filled & sanded. I used white. Did not bother trying to color match.
I have used it to fill old screw holes too.

There is a trick using packing tape that makes it come out glassy smooth

Oh...it is usually better to sand/grind the hole bigger to get clean surface. Don't fill a dirty hole...