I’m not going to put together a how-to for this, instead I’m just going to direct you to some of the coloring tutorials (by artists that are much better than myself) that I’ve used in the past -
Basics of Photoshop Painting by Peter Mohrbacher <— this is a super simple tutorial but it pretty much gives you all you need to know. I usually start my digital paintings with 80% opacity rather than 60%, which is why a lot of my stuff has a chunky cartoon look.
"My Heart" Painting Demo by Peter Mohrbacher <— shows a more detailed example of how to apply the techniques from the Basics video.
Diablo 3 Demon Hunter speedpainting tutorial by Xia Taptara <— I guess I could point you to any speedpainting tutorial on Youtube, but I really like this one. I love watching speedpainting tutorials because they remind me not to start obsessing over the details of a painting too early in the process.
Self Portrait Process by Loish <— I love Loish’s work and it’s really cool to be able to see her process. She inspired me to use a rectangular brush! This is the one I use:
(IDK if that’s the same one Loish uses but it seems to give a similar effect as her work. Also, this is Photoshop CS5.)
Another note on my digital art: I use very few layers. (My most recent instagram WIP is done all on one layer, for example.) At most I’d say I use 3-5 layers, though I’m always merging layers as I go along and decide to keep certain additions. I have tried colorizing black-and-white underpaintings in past work but nowadays I generally keep all layers on Normal mode and just keep painting on top of rough sketches.
Tutorial: Painting with Acrylic Inks by Jenny Dolfen (goldseven) <— pretty much all you need to know about painting with acrylic inks. I love acrylic ink because it looks like watercolor but takes far less time to dry. If you see me most anything that looks like watercolor, it’s probably done in acrylic ink.