Richard here. The epoxy step is just my normal routine in making bows. It takes a little extra time but the results more than worth it.
I always sand the risers to 600 grit, then Scotchbrite pads, and finally OOOO steel wool. I wear a headband magnifier and a bright light to carefully search for any scratches and repair them. Then I use compressed air to blow off any particles. I've always used MAS epoxy in building wooden boats, so that's what I use for my bows. FOLLOW ALL DIRECTIONS! I usually use the calibrated pumps, but when coating risers, I always measure out the proper amount in a small, plastic one ounce medicine cup with calibrations(Amazon)... 2 parts resin plus 1 part hardener. I mark the proper amounts with a fine point Sharpie on the cup, add the epoxy and mix thoroughly. I hold the cup in front of a heat source while mixing, but not too long! Apply with a disposable 1" foam brush (Jenn brand on Ebay) Work quickly, covering all wood areas, but don't worry if you get some on the glass...you can always sand it off. DO NOT PUT THE RISER IN FRONT OF A HEAT SOURCE!! The wood will out-gas and bubbles will occur. Throw out the brush and cup...they are cheap. I found that in my shop, the epoxy will start to cure in ABOUT 45-50+ minutes, but check it frequently by gently touching it (in the fade out area)...you want it to feel like sticky masking tape. Then repeat the application of epoxy. I always apply 4 coats...sometimes 5 just to be sure. If you put on wood grip overlays, coat those also. I always set the bow aside for several days before sanding, to let the epoxy cure. Then sand but DO NOT SAND THROUGH THE EPOXY!! You probably will anyway...if you do, slop a few more coats of epoxy on and be more careful next time. (Photo tutorial to follow shortly)