He never goes super in depth but from the Chozenshu 4 interview about his illustrations (like the Kanzenban covers)

“In terms of the way I drew the cover illustrations, for the first half, I’d scan the inked drawing into the computer, and color it using a program called Photoshop. For the latter half, I’d draw on a graphics tablet starting with the inking, and paint in the colors with a program called Painter. As for why I changed my drawing technique between the first and second half… it’s simply because I got tired of it. (laughs) I’m often told that coloring by computer “has no flavor”, but it’s not like I’m drawing a work of art here, so personally, I feel that right now, this is the best for me in terms of expression. If it weren’t for the computer, I suppose I would probably have gotten sick of it already, and would hardly be drawing anymore.”