Wish I could be in your shoes.
Wow, you do some pretty good work using a mouse. My stuff is terrible. When I can actually do it of course. I use a Mac computer, so I don't have Microsoft Paint. When I get on the computers at school, I use it during my freetime. But I'm planning on getting a tablet and compatible program for my computer so I can start digital stuff.
As for some tips:
-Scan the pics. Usually cameras will make the quality of your pictures bad, including the shading.
-When you're shading, start lightly, and define where you want the lights.
-Sketching lightly first, then outlining harder with pencil, then editing, then finished in pen.
-Color can be painted (A lot harder), done with markers (still hard), colored pencils (Hard for good shading), and just tight pencil (the easiest, in gray scale).