Again, thank you for the compliment! I think you're referring to those Black&White sketches? Most of them were inspired by fighting games in-game illustrations (character portraits/winning pose/kick ass pose/etc).
The actual time of drawing a character in this style is quick for some sketches but usually i spent a lot of time researching and thinking for the right pose and sketch some thumbnails first until i have a clear idea what to draw. In the final drawing, I avoid using fancy brushes (for these sketches in particular) because I just wanted to have fun drawing them and forget about any set of rules to create a great drawing that people cherish. I enjoy moving my hand creating dramatic stroke. The combination of these strokes with the understanding of human anatomy and perspective while drawing will give me the dynamic look I after. Like Yoji Shinkawa's work, he inspired me too.
I enjoy drawing my character the way i did and the look of it (unfinished rough look without color), and prefer them more than my other highly polished finished color work. And I'm so happy that you like them too.