Aloha from Hawaii
I’ve been painting for over 20 years and I found out that due to the tropical weather here in Hawaii really takes a punishment on the wood. I use automotive Bondo to repair termite damage and gouged wood. It hardens in minutes and is a lot better then other wood fillers.
I suggest that you practice this method prior to starting. Also make sure once you apply Bondo always oil prime that area that was repaired. It works wonders.