This process will work on a DSD and Dakota Jakes. It should work on a Avian Jake but I haven't done one of them. Really simple to do paint the area with Rust-Oleum flat black paint. Just a nice thin layer will do. Put the chopped black flock in the strainer and sift it onto the painted area. When done put the decoy over a container and tap on it to get the excess off then put the extra back into the bag to use in the future. I reapply mine every two years. This is all you need for materials.
Flat Black Rust-Oleum (pint)
Cheap kitchen strainer from Walmart
Foam brush
Black chopped felt. I Order mine from Van Dykes Taxidermy supply 1/4 lbs will do many applications.
Hope this helps