What do you guys use to sand down Marine-Tex that you've applied to repair small gouges, etc.? Is a 5 inch orbital sander too much or are the small ones OK. I don't want to destroy the adjacent gel coat.
If the repair is just a small gouge, I always mix gelcoat instead of using Marine-Tex. Gelcoat is easy to wet sand by hand (300/500/1000/1500 grit), which allows you to blend it in without damaging surrounding gelcoat. West Marine has a very nice kind to work with that has the wax mixed in (so it doesn't need to be covered with anything to dry properly). I only use Marine-Tex for structural applications, and then I sand it with a dremel tool or just by hand if it's a smaller area. A 5" orbital sander would be overkill IMHO, unless the repair is quite large.
I'm hardly a Sunfish guy, but I've bone a lot of boat work on other boats........the key to using marine tex, or any other epoxy fillers is to minimize sanding by proper application. When you apply the marine tex, fair it as best you can, and you can really minimize sanding. That stuff is very tough to sand, and is often harder than surrounding material (Gelcoat) meaning that if you aggressively sand it the marinetex will stand proud leaving the surrounding material low. This is why I like to fill a gouge slowly, small layers at a time, until it is fair.
If you have already applied it proud, be very careful sanding the area to avoid damage.