Paint Process for Foam decoys

I know this is an old topic, but it seems to be popular. I just made 3 foam decoys with plastic Herter's heads. I used Zinsser primer. I put on 2 coats in one night. 2 nights later I painted the decoys with Liquitex and Windsor Acrylics. A week later, I sprayed 3 coats each of Krylon Matte finish. One more week later, I brought the 3 decoys out hunting..2 dogris (scaup) and one pintail. I used no weight on the 2 dogris keels; and, on the pintail, I used a full lead strap weight inside the decoy above the wooden keel. After being in and out of the boat, some of the paint on the decoy heads wore off leaving the white primer showing. Plus all 3 decoys bobbed up and down like a fishing cork. I'm sure i'm doing something wrong. SO, what can I do about keeping the paint on better and how much weight do standard sized decoys need on the keel? I bought 30 Herters heads last year and plan to use them up before trying wooden heads. Any help would be greatly appreciated. I am a duck guide in LA, and my customers have already sunk 10 GHG decoys since November with half the season to go. I absolutely must go to foam decoys for next season. 23 seasons and hundreds of dead decoys.