I always use Mas marine epoxy to fill the pores and seal the riser wood. Any two part epoxy will do, but I used Mas epoxy on 6 of the boats I’ve built so I’m used to it and its’ never failed me. I usually sand the riser to 400 grit and blow off the dust with an air compressor. I mix a small amount.....using the pumps that are sold when you buy the epoxy.....stir well and apply the epoxy with a one inch disposable foam brush. Apply it nice and smooth, and don’t worry if you get some on the glass.....you can always sand it off when the epoxy cures. Now wait for the epoxy to harden to the point of masking tape sticky.....about 50 minutes for Mas..depending on the temperature. Then give it another coat, and another, and a final coat, 4 coats should be enough. Don’t let it harden completely between coats.....it should be masking tape sticky when you apply each coat. I usually wait two days for the epoxy to cure before sanding. Then sand with 220-320-400, but DO NOT sand thru the epoxy coats! Be careful....go slow..take your time. Then spray on any finish you like.....I just use Minwax oil based poly in a rattle can, but sometimes K2 Spray Max for a hard, high gloss finish. (On line or auto paint store) Have fun! Richard