Why do you want to lay mat? There would have been no structural component in the gel, if indeed it ever had any. Just scrub it all with TSP and repaint it. If you must have a fair surface, then fill and sand with epoxy after cleaning/sanding. But don't grind away the 'mesh'... that IS structural.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"