Not saying this is perfect but after scrapeing & cleaning them well I prime them with KILZ 2 primer and let them set a few days. Haven't found a decoy surface that this doesn't work on. Flat black, white and dark brown latex can be picked up at any good hardware store. They can also custom make or change the colors for you if you ask. Black and white mixed will get you any shade of grey you may need. Head, odd body and bill colors I get from Herter's (Cabela's now), easier than trying to mix from scratch. You can blend most any combo to get whatever variation you may want. The thing with most any paint is to do it during the summer, curing out, not dry to the touch is the way to make it last. ~~ If you want to use oil based paints buy them without being stirred. Poor off the oil on top and add paint thinner, makes for a much flatter paint job. Latex is easier to use and clean up though.
First it rained, then it blew, then it frizz, then it snew --- from an oldtimers gunning boat ~~ He understood what it's about!