I have used Mr. Surfacer 1000 and 1500 as a primer under Tamiya lacquers and acrylics with no compatibility issues. In fact I find the 1500 applied with an air brush lays down beautifully smooth. Perhaps it's the pigment size or a different chemistry in the Mr. Surfacer 500? I think the lower number Mr. Surfacer, such as 400 and 500 are intended as "fillers" for seams and surface imperfections and then need an additional coat of a finer grade primer before the color coat.