Ive been flocking decoys since before flocking came out on production decoys.
I've also done flocking for people as a hobby/part time job in the off season.
I've always just done heads/tails in black. And last year started doing green on mallards. flocking can only be so durable, and it will scuff and wear if you treat it like a nonflocked head. Same goes for FFD decoys. I recomend slotted bags.
If your treat flocking right it will last many seasons. I had 2 dozen shells I hunted hard over for 4 years. I removed the heads and kept them in a burlap sack after each hunt. After 4 seasons they were scuffed some and did show wear, but still looked new from 20 yards.
Hope this answers any of your questions!
Aim for their lips...