I was trying to paint some plastic stuff under the hood

ex. fuse box cover

had it blue then i tried to paint it black and the paint just bubles and doesnt stick

yes it was dry,clean and the same type of paint

 

get some fine sand paper and sand it down first of use some kind of primer on top of the blue

 

paint remover ( on plastic im not sure)

but will primer stick i dont want to waste another 4 bucks

 

Paint remover will probably melt the plastic also. Try sanding the old paint off. Also the bubbling could be from using one paint that's not compatible w/ the other paint or using too thick of coats. Could be 10 other things also.