If its not real deep what you do is get some gel coat from BCB and buy some MEKP catalyst at Wally World. I think its like 12-14 drops per oz. Id tape your edges, brush some on, cover it with visquene?(sp) and let it set up. Should get hard in a few hours. Any tackiness can be removed with acetone. Remove plastic and repeat until it is a little taller than the gelcoat around it. Then Id hit it with a little 600, then 1000, then 1200 wet sand by hand. Then Id magic erase it hard. Then Id buff it with some liquid rubbing compound followed by good wax. Id get it waterproof the first day and then work the sanding the next day or so. The easy way is to get some marine tex, mix and let it set up. The problem with marine tex for me is that its hard to set it up lower than the surrounding gelcoat and then apply enough gel coat that when you start sanding it doesnt sand down to the marine tex which isnt going to be perfect match in color. Building it up with gelcoat gives you plenty of base to sand to match. BTW- its a lot of elbow grease. You outta try doing it to the bottom of a friends boat… I am new at this but seem to be getting more and more experience. If this doctor gig ever falls through I think Ill hit up Gary Wright for apprenticeship.C.O.D. Jr. III