Over the past three years I’ve repainted most of my decoys. While this only amounted to about 37 dekes of varying species it was some job. Quite the learning experience too. I’ve painted both plastic and styro-foam decoys. I’m sure mallard decoys painted like bluebills would work fine at a distance. Up close a wary bird may not like the different head and bill shape. Also the tail area is a concern. The drake mallards tail has an upward curl while the divers have a smooth tail which slopes off for less resistance when swimming submerged.
Regarding decoy painting in general, the first issue is paint. I’m not up on the technical names and grades of paints so forgive any ignorance displayed concerning what something is called. While you can often get away with using a good quality oil based or epoxy paint from the hardware store, I recommend spending the money to buy Decoy paints.
I have used the hardware store expoy primers for , grays, whites and blacks. They seem to work better on the styro-foam then the plastic, but are acceptable on them. I used these for my styro-foam bluebill and goldeneye decoys and they worked quite well overall. I didn’t have to do the heads on the goldeneye's though. I’ve also used them on old plastic goose decoys of varying brands. One problem is the flat black has too much shine when applied to plastic or another ‘smooth’ surface, so I got a can of ‘Dull Coat” from the hobby shop and it looks ok now. The gray will get a little shiny sometimes too. Hit it with the Dull Coat and its fine. As long as you don’t have to cover everything with Dull Coat the hardware store paints are often cheaper.
From those three basic colors you can do drake bluebills. For the bill just start with the light gray primer and add small amounts of black until it takes on that blueish gray look. I used these three colors of hardware store paint for all of my drake bluebills and the real ones love them. They are old Herters styro-foam decoys and I only had to use the Dull Coat on the heads where I painted them black.
Decoy paints cost more, but give superior results when non-basic colors are needed. They almost never need Dull Coat either so even for the basic colors they are better in that respect. If you plan to paint a lot of one particular species I recommend getting a paint kit. My first kit was of the Parker brand for mallards. Worked great! I have to do minimal touch up on some of them every year, but for the most part they are good to go. Note here: If you are painting up old styro-foam decoys buy a slotted decoy bag for them. I threw mine in a regular bag and they got beat up to the point that beautiful paint job was going south fast. If you find you run out of one color or the other faster then some you can always buy just that color. Cabella’s is a good resource for paints both in kits and individually. I’m sure there are other places to get then too.
One thing I will caution you on is: Don’t take the color scheme from the kit, or anywhere else similar, as the final authority. I have come up with more realistic looking decoys by using a variety of sources to determine the color scheme. I start with what the kit says, then I look through a decoy catalog. Then I break out the bird book. I’ll look at photos of the species I’m painting and look at the duck ID websites also. I then combine all this information, take stock of the colors I have, and start painting. Don’t be afraid to do a little paint mixing to come up with that perfect color. There are lots of little tricks to paint “texturing” too. Like using a base coat of one color then applying a light coat via dry brushing over the top of it. Helps give the decoy the illusion of feathers rather then a flat color. Another trick I picked up concerns painting plastic dekes. Thin the base coat slightly with paint thinner and apply it so it runs into the gaps/depression on the decoy. Then gently blot dry the high spots with a paper towel. When the paint in the low spots dries, dry brush the top color gently so that the paint is only applied to the high spots. This really helps give it a textured, 3-D look. Even on a cheap old, poorly molded plastic decoy.
Finally, when you have something that you think looks funny, set it down and step back 10-15 feet or so. What does it look like now. Very often a pattern or color scheme will not look right up close, especially if you’ve been sitting there painting for over an hour. This happened to me while doing some hen mallards. I got done apply the ‘feather’ pattern and thought, “this looks like crap! No way is a bird going to come into this.”. I set it down on the bench and got up to stretch my legs. When I walked back into the garage after my break and saw it from a distance it looked right. And yes, the birds do come into it, and often.
Well I’m gonna stop before I have enough for a book. Hope this helps!