I think this is what you want to do.
And it is an Oil wash, because solvents are much thinner than water and get into the nookiest of cranies.
https://www.youtube.com/watch?v=r8Oz33NuoPY
10:00 on wards ---->
He uses arcylic wash and oil wash in his work
Plasimo is good, but cotton swab cleaning doesn't work for me because tiny
DE snag on cotton unlike flat vehicle surface.
Or you could try this: Surface is sprayed with a light solvent that is thinner than water, like isopropanol alchohol (I hope it is diluted enough! as it will break down acrylic paint, not as instant as acetone but it will) And then water based paint is applied so it can flow into every noock and crany.
https://www.youtube.com/watch?v=vxhZ7uE7glY
12:53 on wards ---->
I know this example is the terrain, but I think it illustrates the concept. I used to pre wet the model with water, and then try to apply the wash or paint.
Have fun experimenting