Cabelas sells the stuff, G&H makes a decoy paint kit as well. The prep is the biggest process, just like most other painting projects. I would try a few different primers, and paints, to see what works best. I think Cornbread does quite a bit of painting on his decoys. at least from what I remember. Plastic primer in the rattle can might work ok.
You might be surprised how good latex house paint works… The old timers only used house paint. The new latex primers and exterior paints stick so well, they are hard to clean off your skin. These are water based paints too. They clean up with water which is a blessing! I even have heard of boat builders using them on boat hulls they work so well! I make decoys and that is all I use for wood decoys. I have an old set of Flambau water keels that are so light I will never part with them and they have been painted with latex paint too and it holds up. Plus other plastic decoys I own too.