Also could be that you didn't let the hood dry long enough after wet sanding it, you might want to give it a good couple of hours for the primer coat and the plastic to thoroughly dry out, even the slightest bit of water will make it difficult for the paint to stick... and cause cracking...
Bah! release is the bane of good paint jobs... but using the above technique as robertburns suggested will help in getting rid of the release..
I do paint jobs in this order.....
DRY Sand with a fine grit sand paper... Until the "shiny sheen is gone"
Wash the body with dish detergent and rinse
WET Sand with a finer grit sand paper
Let dry for a good 4 hours, sometimes over night...
Shoot your primer coat..... Let sit over night...
Depending on how that primer coat came out, I will either Wet Sand again with an even finer sand paper and wait for another 4-8 hours.... or I directly paint my final coat....
Make sure your rattle cans are thoroughly shaken before you paint... "Personally I would shake them for at least 5 minutes to ensure good mixture of paint inside the can...
The one secret I can tell you is that nothing should be rushed... patience and time are your best friends when it comes to a final finished paint job.
>Start Spraying here><--------------MODEL-------------><Stop spraying here<