It's time to start washing up, It's the only way to get truly grungy! Of course I mean it's time to start applying weathering washes. There are still a few more pipes and other details to add but having some parts looking newer with less weathering will just add to the overall story. And weathering is all about communicating story. Where it's been, how it.s been maintained, the battles fought...
Prior to applying the washes I sealed the existing paint with an overall light coat of Viejo water-based satin polyurethane clear. This just prevents the washes from having too much of a "staining" effect. While I prefer to used water based acrylics for the color coats, oil based paints are my choice for washes. Water based washes just aren't as workable and tend to look blotchy when dry. Oil based washes dry smooth and can be remoistened with thinner and manipulated even after several hours or even a day or two. For the first, overall wash I used my favorite go-to paint for washes, Testors Rubber flat enamel. It's a dark blackish-brown that's an almost perfect wash color for every project. I like this paint for washes so much that I nicknamed it "God's Own Wash" and always have a jar of it mixed up and on hand. For the thinner i use turpentine. I find it gives a smoother result than regular paint thinner. Oder-less Mineral Spirits are a good second choice if you don't like the turp smell. The wash isn't so much thinned down paint as it is thinner tinted with paint. I can't say the exact proportions, too thin and it'll not have much effect, to thick and it'll be hard to remove the excess.
The fist step for applying the wash is to pre-moisten the area to be worked with some clean thinner. This will help prevent staining and aides in wiping off excess stain. Following the clean thinner I mop on the wash pretty liberally, working it down into the nooks and crannies. then almost immediately wipe off the excess wash with a clean cotton rag removing it from the high spots as much as possible. Sometimes i'll moisten the rag slightly with thinner if necessary. You can also use a small brush moistened with clean thinner to remove was from high spots. The trick is to let the wash accumulate in the inside corners and not on the flats and high spots, although it will have a bit of tinting effect on those areas as well.
Here you can see the effect of the overall wash apply to the wing on the left and without on the wing on the right.
I continued on to apply this basic wash to the entire model including the painted engine and fuselage sections.
Once the overall wash was done I went back in and started applying more concentrated detail washes. These will be in a variety of colors to add to the grunginess. For these washes I like to work with regular artist's tube oil paints. These type of oils can be worked and blended for hours, even days as they take a long, long time to fully dry. To apply these washes, rather than premix with thinner I'll squeeze out a little dab of paint on a pallet and then mix in a little thinner with a small brush. Having pre-moistened the area to be worked as before, I'll apply little concentrated dabs of paint down in the recesses and then blend them out with a second brush dipped in thinner. In some areas the paint will stay quite concentrated, in others it'll be blended out quite thin. The first color I'm applying is "Starship Filth" from Mig Productions 502 Abteilung. Yes, a company actually makes a paint color called "Starship Filth"! It's a kind of purply oily filthy black color, perfect for the look of built up oil and grease, You can get a similar color mixing regular black and brown and purple but it's kind of convienent this way.
Here's a before and after of one section with the Starship Filth applied. This area will get more detail washes of other colors, probably some rusts and yellows, and as I said, I can go back and continue to edit and blend out the oil paint with thinner and a brush for a few days before it's too dry.