It is the one which made it to the thing which was easy to use (personally) as for the pen putting opaque watercolor the brush CLIP STUDIO.
I use it in the pen putting when I paint it like thick coating, but may be usable even in rough etc.
The concentration and the fineness change by pressure.
The sample which I painted easily (the oil paint flat brush with the standard coating)
クリスタの不透明水彩筆を弄り、ペン入れ用として(個人的に)使いやすい物にしたやつです。
厚塗りっぽい塗りをする時のペン入れで使っていますが、ラフなどでも使えるかもしれません。
筆圧で濃度も細さもそれなりに変わります。
↓簡単に塗ったサンプル(塗りは標準搭載の油彩平筆)