Washes

Washes are used to put accents on certain parts of a model. Mostly it's used to accentuate (recessed) panel lines. By loading a paintbrush with a little of the solution, then touching the tip of the brush to the edge of a panel line, something called "capillary action" will draw the solution into the entire line.

(Capillary attraction: the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity)

I have two types of washes to try. 

One is the AK Interactive desert dust wash I used on the rubber tracks (see earlier post). This beautifully flows around all the details of whatever you're touching your paintbrush to. This one is dissolved in "White spirit" (also called "Mineral spirits", I believe).

The second is the Vallejo black wash, which is water based. I used it before to dirty up the floor of the Puma's interior. There's almost no capillary action happening here, it tries to stay together as a big drop. You really have to brush it where you want it.

I applied the black one on everything that looks like it might get dirty.

Left : applying the wash on all the details.
Right : removed excess fluid with a piece of cloth.