I'm definitely not new to Photoshop but I've mostly used it for adjusting scanned traditional art over the years so my skills on other areas are rusty. I decided to try a few of the techniques shown here to edit a traditional artwork I finished recently for another course.
Here's the original artwork. Painted with watercolors and colored pencils. The image was scanned in at 300DPI and went through a Levels, Brightness/Contrast and Hue/Saturation pass.
Here's the digitally edited version. I added little fireflies on a new layer with the Gradient tool. Added some photo textures to the tortoise's shell and on the grass under him with layer masks. Then I added the Paint Daubs filter on the original painting layer using the Wide Sharp - brush type.
I'm actually surprised how subtle the effects can be. I might consider using mixed-media techniques like this in the future!