Originally Posted by e3NiNe

he does this technique called "dry brushing". It's dipping your brush in paint, then removing almost all paint from it, before applying on the toy.

It gives a weathered look in the direction you stroke in.

Most repaints look pretty awful because the paint just doesn't stick to the plastic well. His method provides a near flawless look. He can make seams look dirty and add many intentional flaws to the paint.