this could also happen if you didnt rince all the soap off. something to do is get a chemical called hi-solve and clean everything off with it thats gonna get painted. it will get rid of all the grease on the surface and will probably fix your problem

 

dude this is wut you do, sanding with 400 is good, but keep going all the way up to 1000 at least if not 2000. then you go over it with a tack cloth, it's a special cloth used in autobody right before you paint it(after you cleaned it) to get all the small particles off of it, then you apply self etching primer that'll adhere better to anything. then you wetsand it with 800 grit and then wetsand with 1000, because orange peel starts in the primer, not the actual paint and works its way up.

 

that would cause fish eyes, wax and grease remover works well to prevent that