The thickness actually helps
when you are covering with 5 or 6 oz woven cloth because it takes less
coats to fill the weave.

Glenn's giving you good advice on epoxy here. I've had the same exp with FGCI.
It's higher viscosity than many others. I use it fine on 8 oz cloth & below
and layup in a mold is nice too. It's very forgiving of mixing. Be sure to
squeegee. I like to use it in cooler weather 75 to give me a little more time
to do that.
Greg Sefton