I'm not the painter, but it looks like a combination of freehand linework, such as the yellow and black stripes; decals, such as the number, and fine linework in the seams from either an extremely fine detail brush with a steady hand, or a fine tipped micron pen such as a Rapidograph brand. This produces clean looking parade paint schemes such as this one, without bogging the mini down with too much detail and shading. I like.
