Don't search the F-boat groups, the answer is:
Sunrise Yacht Products, aka multihullnets dot com, carries what they call "Net Paint
." it's a vinyl coating that you just paint on. I don't see it listed at their site, but I did get my can of net paint from them. It's good stuff.
It's messy, so unless you're very patient, you'll want to either cover your hulls to prevent drips on them, or pull your nets to paint them. I used to paint my F-boat's nets by laying them on a drop cloth, painting one side at a time. The stuff takes a bit of time to cure, so you can let it dry to the touch, and then install the nets for stretching for full cure (don't walk on 'em till cured). Honestly, though, I don't know there's that much in the whole stretching thing - the paint is very flexible