An idea:
I haven't done this so YMMV.

If you're trying to reconstruct a failed deck core, and the boat can be
turned upside down, then you can cut out the inner skin and the pulpy core
and construct a new core and inner skin working DOWN. If that's not
practical, how about laying the boat over on its side? Wallpaper is not an
impossible PITA.

Working overhead, I've had a lot of trouble in relying on stickyness of
resin.
If you really have to work overhead, I'd try very hard to devise a vacuum
bagging method. The conventional arrangement of laminate|peel
ply|bleeder-breather|bag depends on gravity to keep the resin and air where
they should be, if there's a choice. Invert it and you'll end up with airy
laminate and saturated bleeder-breather. NG! Maybe substitute a thin
transfer medium for the b-b or leave it out and suck from the top side
through perforations? THis could get complicated.

Of course, the practical solution is to cut out the top skin, re-laminate
working down, as the god of gravity intended, and finish with a gritty paint.

Thanks guys, I was asking for a friend. I haven't seen the project
yet. Would there be any advantage to thickening the resin?

jsheesley wrote:

Thanks guys, I was asking for a friend. I haven't seen the project
yet. Would there be any advantage to thickening the resin?

Oh, yes! Moisten the area first with thin stuff, then lay on the
glass or butter on the bog. You must decide on a method for applying
pressure overhead. Blocks, props, plywood and a garbage bag of air
or a wad of soft foam with plastic sheet parting membrane are not as
good as a real vacuum bag, but mucho better than nought.

It is very difficult to apply vacuum overhead with a porous border
to seal the vacuum to. You could 'paint' on a sealing zone.

Terry K