Thinning epoxy with a solvent changes it's properties negatively. Too much thinner and it can shrink, crack, and lift at a later date. Most epoxy vendors do not recommend solvent thinners, specifically cautioning against them. POR tank sealer comes out of the can in a suitable thickness. Depending on cure time, the tank and epoxy could be heated to thin it out without bad #$%* happening later down the road. Both POR and epoxy may be mucked up in the right hands. In my experience those hands are usually attached the same body as the vocal cords cursing tank liners.
