I am glad you like it, photoshop is a great complement for sketching (maybe too good) I basically go over the Image Adjustment Menu Items one by one and move the sliders until I get what I want,and keep the History panel open in case I need to back track.
In most cases starting with a scanned drawing I start with brightness and contrast, that's where the bulk of corrections are done, exposure, levels come next, Vibrance,Hue/Saturation and Color Balance are more drastic and change the colors of the original drawing, I don't like using Dodge and Burn ( for Highlights and Shading) on analog drawings because it takes away from figuring out these things on paper, but the idea is that you can add or supplement shading,shadows and highlights with them. ( I only used a little burn to mute the bottom front corner).
Like anything, practice makes you faster, I think I spend about a couple of minutes or so per sketch or photo - I've done 100's on a sitting for some projects, also any keyboard shortcut you can learn will make you faster.
If you get stuck, plenty of folks here use it, so they might also have their tricks and tips.
Cheers, and Happy T-day.