So I've been a Photoshop user for drawings for a good three or so years, and a few weeks ago I got Clip Studio Paint. I think they both have their pros a cons from each other, but there was one brush (or specifically brush setting) in CSP that I hoped might be in Photoshop.
So in this video here at 20 seconds in the artists selects the smooth water-colour brush which can add paint, but if stroked lightly it only blurs already existing paint. But in a more subtle and controllable way than the smudge or blur tool, which in my experience are a little unwieldy and often look messy for shading. I tried this smooth water-colour brush for shading in a recent drawing and it was one the easiest and most efficiant and good-looking ways of gradient shading I've done.
I'm not quite sure which setting or, more likely, combination of settings allow the brush to do this. But, I was wondering if there was a selection of settings or, better yet, a defualt brush or downloadable brush (like one of Kyle's brushes) that do this function?
Photoshop is an Image editor that has some painting tools like paint brushes. Why not try Adobe printing application like Fresco. There is a forum for Fresco try asking about its brush painting features and brushes over there. From what I have seen it seems to have good oil and water color paint support. Fresco Forum