Shaping a 6'4" shortboard

Working on a shortboard, 6’4", still have the rails to blend.  I’m really happy with how it came out so far.  Shaped from 1.85lb block foam EPS with a ply stringer.

I have a few nicks on it and in the past I have been sealing my boards with spackle.  I plan on doing some paint on it so I was thinking the paint could seal the board.   I was wondering could I get away with not sealing it with spackle if I sand the surface of the EPS really smooth, and painting it.  Thoughts?  Thanks