Well, there are not many options that I am aware of. I have not dealt with redcoat, but you can try acetone or MEK to dissolve it. If that doesn't work, it will probably have to be baked out. Here is a link to a place I have used, and they are A No.1 in process and quality:http://www.gas-tank.com/
they are not cheap, but they are not outrageous either for what they do. Their work and the result are top notch. Your wallet will have to dictate your way to go.