A Technique for Creating Mottled Paint Effects
Here's a quick and inexpensive way to achieve mottled paint effects like you would see on US Navy aircraft.
I discovered that coarse, open cell aquarium filter material works really well. I initially used a half dollar sized piece on the Mi-6 rotor blades that you saw in a previous post, but this time I found another filter that I bought years ago for another technique I never tried. This particular material has a little smaller cell structure, but works just as well.
The first step is took cut slices off the block of filter. I tried a large kitchen knife, first, but that didn't work too well. I opted for scissors and although not ideal, works pretty well. I trimmed the thickness as uniform as possible, but that's not too critical. The object here is to get as much randomness as possible while allowing enough paint to get through. I ended up with about 1/8" (3mm) thick pieces.
After putting down your primer, sand it lightly with a 1000 grit sanding sponge. I used one made by Tamiya. This will give you a nice porcelain-like finish. I didn't do that for this example because this is a part from a cheap Chinese knock-off kit that has a really grainy texture. I did sand it with 600 grit to prep it a little. I then sprayed it with Mission Models Paints Neutral Gray darkened with a drop of black to exaggerate the contrast for these photos. It actually worked well enough for a real model.
Next, I mixed up some Neutral gray and added white to it at about 1:1. Once again, for contrast. You can mix your paints to taste. I placed the filter material on top and sprayed the lightened color. You can spray light coats, heavy coats or both. Randomness is the key. I would suggest holding the filter material slightly above the part.
Here you can see the first light colored mottling cat. I let that dry for a few minutes then rubbed it down with a lint free paper towel that I purchased at a plastic supply store. I'm sure Amazon carries them, too.
I find that rubbing down the paint blends some shades together very slightly it also helps to kill the roughness that builds up with matte paints. I usually rubbed down my models to a semigloss sheen that is good enough to apply decals onto without a clear coat (I hate clear coats and I don't know why).
You can repeat the mottling process using a darkened version of the base coat. Here I used the already darkened MMP Neutral Gray and added 3 more drops of black to it.
The pattern here looks a little repetitive even though it's not, and you can prevent that by holding the filter 1/8" (3mm) above the part you are painting and moving it around slightly while you spray.