One trick is to lay a piece of plastic that is about the thickness of a ziplock sandwich bag over the repair and squeegee the air and excess resin out. There won't be much sanding to do after it hardens if you put the right amount of fibers in the repair. You would prooly want to tape off the repair area to protect the good part of the project. You can also trim the repair when it is partially hard to save time later on.
polyester won't go off when put over some types of epoxy. You can put pigment in surfboard epoxy, or just spray paint the repair for cosmetic purposes.
Also i have found that the most durable bog is a mix of aerosil, a little bit of finely cut up carbon, and epoxy. Works great on the bottoms and foil tips.
The rule for kevlar is bury it deep. It soaks up water and only forms a mechanical bond whereas carbon forms a chemical bond with the epoxy.