: Pedro,

: I did an initial sand with a random orbit sander with 60 grit. I think, based
: on your advice, I will do more with my fairing board and 80 grit. As far
: as my choice of underdeck filler, I've decided to play it safe and use a
: microballoon-based epoxy filler mix (west system 407). As for the few
: small cracks on the outside (maybe more after additional sanding) I've
: been experimenting with Elmers (water-based) red oak wood fill and it
: looks pretty good.

: Thanks for the advice everyone. This forum is great!!!

Dave,

Your choice of fillers sounds good to me. Just remember, sand only as much as you need. If you have gaps on the inside, the more you fair and sand the outside the more the gaps will open up.

Pedro