The stuff is hard to sand
I blocked the roof for over four hours with 400 last night and all I was able to do is knock most of the texture off of it. I used the 1104 in the past with a conventional gun, which is a medium gray and it sands fairly easily. Now I switched to the 1107, which is a dark gray, and I applied it with a HVLP gun. The darker stuff seems harder than the lighter colored stuff to sand. I switched to the darker color because I plan on using a dark base coat. Could it be the URO, types of activator or reducer, or maybe something atmospherical?