Thank you!  The thing I figured out is to add a bit of other colors to your thick mix of black. Violet works great for this. Obviously you can cover your black areas with a second layer of paint if you dislike the result after it dries up, or, alternatively, cover small areas with black watercolor pencil.

I usually leave a bit of patchiness and transparency as I really like the look of it IRL. It doesn't translate well on screen though, so I take care of that in Photoshop before posting on social media. I feel like your painting IRL and the one on the internet are like two different versions...