Okay, I am intrigued by this product and it's effectiveness. I can see it being possibly being useful for minor fills and seam correction, such as engine block halves or seat halves. Maybe even being used as a spot filler for say... errant marks left behind after panel scribing for deepening door lines. I know there are two types. Which would be the best all around to have on the workbench? How well does it finish down? What paint products react adversely with it? And lastly, where would be the best place to source it? Thank in advance!