I spent quite a bit of time experimenting with washes on scraps that I detailed and scribed.
Crushed pastel chalk in liquid medium was too “chunky”. It always looked dotted and didn’t flow well. Some liquids, even with wetting agents just didn’t dry well. Ick.
Dry brushing didn’t work well. It took a long time before you noticed that it was too dark and by then it was not fixable.
During the course of things I made the decision not to use a flat coat after paint. Everything I tried dissapointed me or played havoc with the paint. I even tried the vaunted “Future” and Tamiya flat base, but could never get it flat enough without going milky. There was no chance I was going to risk it. So without a final flat coat, I had to stay away from dry brushing and anything that couldn’t seal on it’s own.
I really liked how a was turned out. A drop or two of my base paint darkened with a drop of Blue Angle Blue and thinned with 10 ml of thinner worked very well. It darkened surfaces sufficiently and flowed well and could be blotted if it got out of control. Two or three passes worked well on areas that needed “separation” from flat surfaces. I was really happy with this.