Paint Question

I'm new to this forum and I'm really excited about the progress I have made on my armor so far. I'll give you guys a little bit of a back-story. My armor is made from a trash can, and I am using the satin finish paint. So far, I have painted the green on, but NOW its time for the yellow.

Everytime I do the yellow though, it either cracks the green, runs, or does many other crazy things. Is there a specific kind of paint that I need, is my technique off, or is that just normal? I'm really sorry if this is a ridiculous question, but its hard for me to progress if I can't get that yellow on.

Thanks!

Well,
Are you using enamel or acrylic? Spray or bottle?
The type of plastic those trashcans are made out of isn't the greatest for paint adhesion. For that type of plastic, I'd recommend giving it a good once-over with some medium grit sandpaper, then use a couple of coats of primer before laying down your base color.
If you're using enamel yellow over acrylic green (or vice versa) it could be causing a reaction.
Make sure your green coat is really dry (like 2 or 3 days) before you apply the next color.

You can paint acrylic over enamel with no problems but you can't use enamel on top of acrylic at all

Well, I'm using spraypaint for both layers, but I think I have the advice I need. I think I should just wait a couple of days.

Thanks!