I come in peace.
I am not someone that knows of painting by any means. When I bought my car someone apparently just sprayed a coat of body color paint onto the block. It looked great until I started driving the car. Then the paint all started to peel off.
After about 3 years, my block was bare.
I know POR-15 has been getting beat to a pulp here, but I went with one of their paint kits. There was a degreaser, then something after that... Maybe an alkaline solution. My memory is failing me now.
Anyway, I have had the paint on the block for 4 years now with no signs of trouble. I did buy the brush on paint, and it takes two coats.
I guess my point is, it's all in the preparation.