W2, if you go to all that trouble , might as well Fiberglass the whole thing
How so ?
Laminating is several orders of magnitude more of a commitment and skill level than slapping on some putty and knocking down the highs with a homemade 80G longboard.
If anything, an epoxy/microballoon mix is the absolute EASIEST thing in the world to do if any sanding is going to be involved. It's only to get a 'yacht finish' that the endless hours of sanding are required...which isn't likely the case here.
If loader doesn't want to go for sanding, he can do what wood builders have been doing for a long time and simply use epoxy to fill the weave of the canvas, except that he'll top it with paint rather than varnish or PU for UV protection. That's how the lion's share of cedar strip boats look so sexy - some guys go nuts with wet sanding but mostly it's just more resin to fill the weave and topping with varnish.
Either way he winds up coating his trailer in a membrane that's 100% watertight and weighs next to nothing - that's a win/win no matter how you slice it.
Vacuum bagging on par with rough fairing ?
We all have different experience I guess...