I just followed the way Kubo draws the robes of the shinigamis, I defined an area that I thought was pretty robe like and filled it in, and in the lower area with the folding I just did some really dark hatching. I think that the black really helps contrast the white. So the sword being in front of it was super helpful!

You can definetly do it! Just gotta try it out, make some art and just paint the darker clothes black. You learn by doing man, and time was made to be spent! >;D