Was thinking about this for my garage ceiling. Only need a couple gals so extra cost is not a big deal. Most people rave about the dead flat finish which covers imperfections. However, some say it dries too fast, leaves roller marks and is impossible to touch up. Also must be primed first but I was going to prime anyway. Is the 508 much better (flatter) that Muresco? Is it difficult to use because it dries too fast? I remember talking with my local BM store manager last year about 508. He steered me away from it saying it was difficult to use, especially for DIYer who has never used it before. Thanks.