What paint to use for engine bay?
Over the blasted metal, I would put epoxy etching primer. Then shoot single stage urethane two part paint in the color your car will be.
From what I have experienced TCP global single stage urethane is great.
I put SPI epoxy over blasted metal and the TCP over the epoxy within the time frame where the epoxy is still "hot".
My experience with SPI epoxy it outstanding and I have heard the same from others. Rock solid. I use it on all kinds of stuff that I want to protect long term.