Paint bubbled months later-how to prevent??

Last year I repainted my truck bed, it had minor dings so I sanded bare the areas and did the putty work. Several months later at some of those areas the paint bubbled. I am soon getting ready to paint my project car that also had some minor dings. I have too much time and money in this car for the paint to bubble later. What should I do in my prep to prevent this. The car was mostly stripped down to bare by sanding, no solvent. I have not primered it yet and will be using a filler primer. My truck was done the same way but not striped. The project car will get a base coat of silver metalic and top coat is House of Kolor tangelo orange pearl. Any help appriciated. Mark