Dry brushing is the oldest weathering technique there is and the most unforgiving of the wrong paint. You load a brush, wipe nearly all of it off, and drag what is left across the surface so the colour catches only on raised edges — rivets, plate joints, folds in cloth, the sharp corner of a hatch. Too wet and you get a smear; too dry and nothing transfers.
The colours here are formulated for exactly that: a high pigment load so the small amount left in the bristles still covers, and a fast set so it grips the edge rather than flowing off it. They are also simply good highlighting paints for figures.
Dense acrylic colours sold specifically for dry brushing, covering bright and muted tones as well as oxides, earths and greens, in sizes aimed at frequent use. The range includes strong saturated colours that suit fantasy and wargame subjects alongside the restrained greys and browns used on scale vehicles and aircraft.
Pick up a small amount, then wipe the brush on kitchen paper until it leaves almost no mark. The first stroke on the model should be barely visible. Build the highlight in several passes and you keep control; load the brush heavily and the edge turns into a line of thick paint.
A sharp new round is wasted on this technique, and the technique destroys it. A flat or filbert with a slightly splayed tip spreads the colour across an edge instead of drawing it. Dedicated brushes for this work are in modelling brushes, and keep one aside for dry brushing only.
Highlight with a lighter version of the base rather than with white, which turns everything chalky. For bare metal wear, a dry-brushed metallic paint on step edges and hatch rims is faster than any chipping method and reads well at small scales.
Dry brushing puts light back on raised detail after shading has pushed it down, so it follows washes rather than preceding them. Afterwards, a dusting of pigments or a pass with dry weathering compacts softens anything that came out too bright.
How this fits with the other techniques is set out in weathering products.
