For people who asked, here is a video of the process on youtube
( Sorry, it is not really a sketchy drawing u_u)
I don't know why, but you need to load a little bit at the beginning or skip directly to ~1min if it doesn't want to work.
( Or perhaps my computer is too bad Orz )
It is the first time I am doing a video, please don't hit me.>_<
I'll try to do better next time ;A; ( Any advice are welcome.)
This is how I proceed when I really don't know where I am going with a drawing, and the result is uncertain.
I began with flat colors 'cause I didn't know what I wanted. Then, frequently tools used are pen, airbrush, water, marker.
Tools : sai