thats a great solution Gary. Wish I thought of that. How much over size exactly ? I might continue with my sealant plan this time however as i have not mixed epoxy before. will get prepared to follow your advice when i put it back in next summer. If you were going to choose a white sealant what would it be ? 

Is Rust-Oleum Marine available in NZ?
I know aerosol cans for interior and exterior use.. furniture and stuff, are available.

2 issues here.. paint a boat with aerosols?? really
And 2 pot is the only way to go in 21st century to paint a boat.. or vehicle.
 This a genuine member/ post above?

Back in the day..would be late 60s early 70s, pre 2 pots, pre dulon lacquers, or about when they started to come in,
Dulux produced an enamel car paint.
One would squirt on a thin holding layer, wait 10 mins till would just lift with a finger touch. Then squirt the next coat.
 Just enough to cover or almost cover...
Again wait till lifted with finger touch..
 Then layer it up fast..

That last coat would hold, if you knew what you where doing, no runs or sags orange peel etc
Get out of the room so no air movement , lock it for the next 12 to 16hrs.
 Since it dried slow the paint would flow out over the3 surface to a perfect mirror finish. But would stay tacky for quite a while.. which all meant slow turn around ... but get the hang of it and perfect , no Orange peel etc for the home garage ...
If one did not do the elbow work on blocking down, showed every tiny defect. This is where a good paint job is made or broken.

Then they introduced , from memory Plus1 additive think called, yes a isocynate.. the 1st introduction of isocynate.
mixed art something like 5 or 15% by weight.

Same procedure as above.. same finish...
But 'dry' after 8 to 12hrs, and after 3 to 5 days, real hard.

I didnt think this stuff was still around...
If the same, yep OWT, ideal for the home painter.
I cant emphasis enough that the pre blocking has to be perfect as there is no orange peel, every defect regardless how small sticks out.

Later on Dulux brought out experimentally  a product called Acran.. a full on 2 pot. We where able to play with this stuff in my fiberglass molding factory.. that stuff was hard, harder than modern 2 pots, and flexible for thin fiberglass panels.
 Dont forget your respirators with correct filters thu.

Hmm.... Brush...?
 OK I see where your question is coming from.. your projects.
I have used enamels in classic/,rod engine bays, because they are so forgiving (containants, etc) and flow so well. takes days.
 Some weith a artist brush and air brushing.

The old school guys, before and just when I started doing this stuff, would use paint brushs, bloody good expensive ones, know how to thin down right, and work the brush.. so would flow right out.
 Saw it done once...its not like a gun, far far more skill.
 Guns, are easy, follow the rules exactly...

Even after stripping our last house, plastering to paint finish, I always use3d rollers, even for wood windows cutting in.. small sponge rollers....cause I hate brush marks, espec mine..

So on that background, I was me, I would pick up a smaller top load finish spray gun and if need be hire a larger CFM compressor for a few hrs.
 Every workshop should have a small compressor.. from pumping up tyres , footballs, blowing down benches, to small paint jobs.
You would still be using high build underneath (check product compatibility or you will get into an expensive , time consuming mess.  So even there a spray gun will save a lot of time and money (latter, clean down, expensive brushes etc.)

Oh and in the old school thing, the guys used to clean down brushes with jayes fluid disinfectant...
 And even the hardest, oldest of brushes, dropped in a jar of jayes will come back AS new (not 'like' 'as')
That just popped up from memory...
Jayes is saponified creosote with a bit of resin dissolved in it.. so its basically a soap on super steroids..with organic dissolving properties.

Ok boys n girls. My repair work mixing gelcoat was ok but colour matching not great. So after reading through here,it seems best course of action is to paint. Gelcoat faded with a few scratches that can be faired out. What to paint with?? will be a roller/tipping job. Cant spray here  Colour? Yes its a 1970s gold/yellow and thinking keep the same colour,no need to undercoat?? sand/degreaser wash with acetone?

SaltyC wrote: Talk to these guys they are great. Saw a demo old clinker style fibreglass dinghy they had hal done for demo at one of the on the water boat show. Came up great. They are also more than happy to talk you through it usually: https://altexpaintshop.co.nz/frontend/surfaces.cfm?page=fibreglass

Thanks "SaltyC"  will go to the avondale shop. Very hard trying to talk to numpties at marine shops,just sell product with no Knowledge.