Advice to make a perfect repair, huh? Not sure that's possible, but here's a point in the right direction...

First the surface needs to be aggressively abraded, 36 grit is not too course. If you sanded away the gelcoat that would ideal. This will probably reveal some pinholes, they shouldn't be a problem.

You'll need to use bias-cut cloth to conform to the coaming shape. This can be biax tape (doesn't have the sexy carbon weave look) or diagonal strips cut from regular woven cloth- plain weave or twill. You'll have a lot of waste with the cloth, otherwise known as opportunities to further play with the carbon. Allow at least a couple inches of extra strip width when cutting your diagonal pieces, and consider applying a strip of masking tape to your cut line and cutting through the middle to constrain the loose edge.

Start by wetting the repair area with straight epoxy. It's nice if it has set up for about an hour so it's a little sticky by the time you start to apply the cloth. Use a thickener to make a paste to fill any pinholes with the dregs of this batch of epoxy.

Place a strip of plastic sheeting, a couple inches bigger than your carbon, on a bench. Lay the carbon on top and wet it out, using a plastic spreader. Lift the plastic and check the underside to be sure the carbon is wet all the way through. Leave no standing puddles or glossy sheen of epoxy on the top.

Immediately cover with a similarly bias-cut piece of peel ply, gently dragging your plastic spreader over it to marry it to the carbon. (This can be found in ordinary fabric stores as "nylon sport fabric", and ripstop nylon also works.) Gently roll this 3-layer sheet into a loose burrito, leaving maybe 18" unrolled. Carry to the boat (you masked your work area already, right?) and peel away several inches of the plastic sheeting and begin applying to the coaming. Use your double gloved hands to gently massage the carbon and peel ply to conform to the profile, pull away some more plastic, and advance around the coaming. You may find that the peel ply won't fully conform to the shape, and need to make vertical relief slits in the top and bottom edges- this is fine. When you reach the point where you started, lift up the initial peel ply so it doesn't get sandwiched, then with some sharp (serrated is also nice) scissors cut the end of your strip to length so it overlaps the beginning by an inch or so. Spend some time neatening the peel ply all around, using sort of reverse pinching motions with your fingers and massaging away any wrinkles (still gloved!). This whole cloth process should be doable in less than 20 minutes, so choose your epoxy and working temperature accordingly- i.e., avoid anything really fast, or temperatures that are really hot.

When the epoxy is well into its B stage (time varies with different epoxies), and it has become noticeably stiff but still a little pliable, glove up and cut away any overhangs (that masking taped edge we talked about earlier is hanging over the edge of the coaming, right?), using a sharp utility knife.

The peel ply may be remove able now as well. Grab a corner and give a short sharp 180 degree tug- if it leaves the carbon behind, it's ready. Peel away the rest. You should have a matte, smooth finish with a light cloth texture. If there are no glaring problems, brush on a coat of straight epoxy (it will look 1000% better all of a sudden), let cure, wet sand with 80 grit, apply a second coat and wet sand with 180, then apply a UV protective clear coat such as varnish or automotive 2-part polyurethane available in rattle cans.