From the blog "Mick Bonwick's Blog"

Nearly all of the items weathered in this blog have been attacked by one or more of the following brushes:   Comb 1/2" flat shader Rigger Filbert   The use of these brushes is detailed below, in the sequence they appear in the accompanying photograph.   The comb brush is used to work on paint that has already been applied in order to create uneven streaking. The combination of long and short bristles, when dampened with or dipped in thinner