Go ahead and do the 10-12 coats. Better too many then too few. Make sure you dont get any LR on the fiberglass where you need to seal the glass. I figure that goes without saying but I had to say it anyway.....just in case. On the final 2-3 coats keep the direction of the roller pattern in mind, you will be able to see it when the tank is filled. The smoother the better. I think rolling the last coats on with the roller going horizontal looks best.