What color epoxy are you using? I kind of like the black, so it will show you the dents easier. Then I do any body work needed over the epoxy and use the light gray 2K for blocking.
I have a gallon of grey for underbody and as far as it will go for the first 2 coats. I bought high build and am going to try white since the blue is so light. I like the SPI epoxy for its sheen and dull once sanded. I never used my graphite I bought for the Coronet. The white may not be a great idea for blocking though.
