I highly recommend it. Make sure the wings on your mojos are clean. After a while they get scratched up and the paint gets faded. Paint them with flat spraypaint in the right colors on the off season. It only takes a few minutes to keep them fresh and bright.
I only flock the white parts on hen mallards but on the drakes I do the head, chest,and everything that's white. I also mix up grey paint that's just a wee bit lighter in color than most decoy companies use. The grey paint is for the backs.
Finally I'd do the highlights on the back feathers by lightly dragging a somewhat dry black paintbrush over the top of the grey parts. You know, dip in in black, then paint a paper towel until it's almost done and then do the feathers.
The ridges on the feathers get highlighted by using this technique.
The Arkansas guys that saw my decoys called them "January Mallards" because they don't look like that until late-season.
I think my flocked decoys helped in late season but not so much in the early part. I'm keeping some dinged up ones for early season.