For this step, I used a wood filler and decided to work with a water-based product from Ace Hardware. There are many wood fillers on the market and probably any of them would have been fine. The first layer was pretty thick so I waited a full 24 hours before applying a second layer. I also applied filler to other nicks and scratches on the seat. After the second layer was dry (about 4 more hours) I was able to sand it down.