You have made a lot of progress with Naxos. It looks as though you have a solid framework for planking too.
With regard to resin, I have found ZPoxy very good, not too smelly and easy to sand. Polyester resin is very smelly and unpleasant to use in my humble opinion and will be difficult to finish on the outside. There are water based resins such as Poly-C or EzeKote but they aren't as durable it must be said. I think with a boat like this using glass cloth inside is a bit belt and braces but your choice , of course.
With paint, anything can be used but it is good to stick to one system to avoid any unwanted reaction. I have had the dreaded wrinkles when mixing some sprays with enamels, admittedly years ago now.
On my last model I used two coats of ZPoxy, water based household primer (Dulux!) to build up the surface and then enamel topcoat, in that case Blackfriars, topsides and Humbrol, underbody. Lots of folk use car spray cans exclusively.
Incidentally, there are about three You Tube videos of various Naxos models which you might find interesting if you haven't already found them.
Good luck and watching with interest.😊
All the best,