I used 2 layers of mat in the corners. Did the first let cure then did the second, after it cured I put another top coat of resin. I used Polyester resin and it said it fully cured in 2 hours but I waited a couple of days before doing the epoxy. I did not sand between resin coats but did sand between the resin and epoxy. I used sweetwater epoxy which you have a 4-10 hour window to do the second coat without sanding.