Some things I follow best practice advice. Certainly that has been very well given for your project in the previous responses.
Other things I do to the criteria of good from a durability/safety standpoint, but not really necessary to achieve industry best practice. All depends on the situation and the time/cost/benefit/outcome tradeoff's. Looking at your profile, you've got an O'day. They haven't been made for a while, so likely the original gelcoat is getting long on the tooth. Matching exactly might be difficult. Particularly the gloss/oxidation differences. Here is my work-around which I have done in several spots on my boat. Most notably on my cockpit walls/bulkheads where PO's had mounted various stuff that either was no longer there when I bought the boat or I removed myself.
- Stuff some quick set epoxy into a syringe. With this, you can fill the hole very precisely without any spill-over.
- Work quickly before the epoxy sets up in the syringe.
- Fill the holes so that the epoxy bulges a bit above the surface, but doesn't spill much over the surround surface.
- Practice on a dummy hole first so you get the feel.
- When the epoxy sets up, but before it is hard, it is easy to "saw" off the bulge flush against the surface with a box cutter knife like in the attached url below. You will have a 30 or so minute window when the partial epoxy set-up will be just right. That is still soft but not sticky. With a bit of feel, the surrounding surface will not be damaged.
- With white paint, maybe mixed with a touch of beige paint so that you can approximate your gelcoat color carefully, dab over the epoxied hole using a small tipped artist's brush. (For paint, and this was four years ago -- still going strong, I sprayed some white Appliance Epoxy spray paint into a small container. Then added a touch of almond color spray paint to dampen the harsh white. Let the mixture sit for a couple of minutes in the container to thicken a bit. Then dabbed on over the epoxy.)
The holes covered by this method can be seen either with a slight depression or a slight raise if the angle of light is just right. But really when I'm sitting in my cockpit they don't stand out as unsightly. On my 32 year past new boat, lots of other getting a bit old stuff stands out much more.
http://www.ebay.com/itm/LOT-OF-10-C...593?pt=LH_DefaultDomain_0&hash=item3cc4585f09