My usual approach is to make the fillet as best I can with a shaped filleting tool, and let it cure to an inevitably rough and spikey finish which is as hard as concrete.
This I then dress this to a reasonable profile with a carbide burr before fairing it with more fillet mixture. Lastly this is sanded to a smooth finish, with a sander and by hand.
This is effective but is tedious and very time consuming, and I have always wondered if there is a quicker and better way of making nice, smooth fillets.
I recently watched some instructional videos on the internet on how to use epoxy resin and fibreglass, and discovered something called Peel Ply.
As the name suggests, this is a sheet material which is applied over epoxy resin. When cured you simply peel it off, leaving a flat textured surface ready for the next process.
I decided to try it out, so I made a big fat test fillet on some scrap ply and covered it with a strip of Peel Ply.
I then wetted out the strip with some clear resin and shaped it into a nicely contoured fillet with a hard nylon roller.
This is what it looked like.
Here is the final fillet.
I should of course have removed the blue tape and cleaned it up before applying the Peel Ply, but it's only a test and lesson learned.
I will use Peel Ply to make the remaining fillets on the boat. If I had discovered it earlier I could have saved very many hours shaping fillets, but hey ... as my son tells me when I become discouraged by boatbuilding setbacks: "Don't forget, dad. It's a journey!"