I've never painted a blaster with spraypaint to say one way or another but it's possible the paint reacted poorly with the plastic. Not all paints react well with all plastics, so you may want to consider that.
Also, weather conditions determine drying times on any paint but especially spraypaints like that. I'd look into these factors a bit more maybe. Without knowing the conditions, the plastic type, how the paint reacts, it's tough to tell... It's good to test it on a plastic like you're working on first to see what happens for sure.
In humid conditions though it can take quite a long time to dry too, even if everything else is ideal. Humidity can really make paint do funky things.
Most paints don't cure for at least 24 hours though. Sanding might help but at that small a scale you'd want to be cautious.