I agree with Mr James...that is one thing that crossed my mind when I read the first post...was the "material compatibility"...I am not a chemist so everything is trial and error..lol..when I find a process I like I stick with it... I use tooling surface coat...it works for me...everytime...yes it is tough to sand...80 grit sand paper is my friend...lol...then I will typically work to 240 grit finish...faster or easier is nice...but not if your doing it twice...lol...