Sanding The Inside
Sanding is a tedious but necessary step. It's messy and it takes a long time to go through the entire surface. Every plank, rounded edge, filet and pass-through hole was sanded using 220 grit sanding paper, one section at a time.
I didn't like the way the single centerboard cap looked so I added another 6mm layer of marine plywood with rounded edges and 6mm shorter all around to give it a stepped look.
View of the two step centerboard cap and the jib sheet track stringers.
Another view of the two step centerboard cap and the jib sheet track stringers.
Priming The Inside
Next, I applied the first coat of Interlux two-part PrimeKote primer. Priming the inside is more demanding than the outside. For one, there are many inside angles to cover.
Filleting the joints with the round edge end of the filleting tool definitely was a big help as I applied the primer with a 1/4" radius roller. 
I also used a 1-1/2" badger badge to cover around the floor strengtheners the tight angles.
Before applying the second coat of Interlux PrimeKote primer I fitted the two cleat platforms for the main sheet hoop controls over the thwart. Made from the same hardwood stock as the one I used for the crew floor stringers, I glued the cleats to the thwart using epoxy resin mixed with with colloidal silica.
The precise location for the cleats and all other interior parts can be found in the Interior Construction and Layout drawing from designer Keith Callaghan.
Lastly, I fitted a hardwood mounting block for the mainsheet swivel jammer.
Next, I applied the second coat of Interlux PrimeKote primer. It was just as challenging as the first one. 
Aft view after priming.
Having applied only the first coat of primer to the foils, I proceeded to apply the second coat of primer to the rudder...
...and to the centerboard.
Thank you for visiting!
Fair winds and happy sailing!
