I flipped and sanded. If you took it apart you would need to get it all lined up again before sanding the other half in the future.

I sanded deck and hull before splitting it apart. Then I pulled off the deck and glassed the outside of the hull. Then took off the hull, put the deck on and glassed the outside of it. Then sanded the inside of both halves. Then glassed the insides.

Warning: Try to keep the deck and hull on the forms as much as possible. On my second boat, I had to go out of town for a couple weeks after glassing the insides. It was not really too much trouble mating the two halves but they had changed shape. The issue came when I cut the deck hatch openings/covers. Becasue I had forced the deck to match the hull, the hatch pieces I cut out changed shape (they were "sprung"). I had to put them under tension and apply more fg to the insides to bring them back to a curve that matched the deck.

Dwight