After fibreglass and primer coat
See test I just did for my fish cutter 'Gina 2'.
Cheers, Doug 😎
PS: seal and prime the hull when you wish, I do final finishing / polishing when all major internal works are done, and especially after prop shaft tubes and rudder stock are fitted and 'fettled in'.
Cheers, Doug 😎
PS Applies just as well to renovations and new builds!
BUT more power to your elbow for scratch building 👍