I painted the entire thing with a brush using Vallejo paint. I wanted to see the Zaku's color variations, so I tried painting it myself.
Vallejo paint is amazing because it doesn't leave any unevenness even when applied with a brush.
The paint is more likely to peel off than with lacquer, but as long as you don't touch it until after applying the top coat, it should be fine.
I top coated it with water-based matte clear paint.
I also applied it before spraying on the matte finish.

Gouf Custom Zaku Color | やんまー's Gunpla works