Probably has been posted before, but I have started using a product called Goof Off. Stuff works great. One thing that I found would clean my brushes after applying Mr.Surfacer. Have not tried it to see if it would work as a thinner such that you could spray it. Would probably test it on paint to make sure its not too hot. It works great on cleaning acrylics. I have a paint cup type tray that I use a bunch to mix paints and doesnt matter if their dried - this stuff removes it. Seems to work on enamels as well. One word of caution. In my picture you can see my green mat. Some dropped on the mat and it removed the yellow marking lines. Anyway - I love it. Hope you find it useful. I bought mine at Lowes. I think it was under $5.00

I may have trouble with the image. I always do. Here goes.

http://i1149.photobucket.com/albums/o587/deerbill/P8190014.jpg