I was having a conversation with a friend who is very familiar with vector graphics, and he wants to learn to draw more freely as I do. Even though I'm moving slowly away from software that is mainly for vector graphics (Illustrator), I am making this journal to teach others my styles in vector applications. I hope you find this helpful.
1. Using Vectors (Illustrator)
Before beginning, it is recommended that you use the pencil tool. Any strokes you create with the brush tool will be changed later on.
A. Unless you'll be printing, work in RGB so the colors are not so dull. (File > Color Mode > RGB)
B. Work with larger layer thumbnails. (Flyout menu > Layer Options > 50)
Draw something as if you would draw it on paper (open paths), but make sure those paths overlap each other.
Tip: Press Control/Command + Shift + A to quickly deselect paths you don't want connected in your next stroke. (The control in Illustrator is very picky. Closure and sharp corners can ruin the path you just drew.)
Now select all of those paths, and use the Live Paint Bucket tool to group them together, and then use it again to fill it in with color.
Tip: Anything you draw extra that you want to have be part of that group can be accessed through the layers. Expand your layer and just click and drag your extra paths into the Live Paint group.
To add shading, draw your your borderline separating the shade from light on your drawing, and make sure that no fill is applied. (Have your line a smaller line width so it stands out.)
In the layers panel, click and drag those lines into the Live Paint Group.
Hidden under the Move tool is the Group Selection tool. It can transform and select individual paths even though they are grouped. Use that tool to select each line, and make sure that no stroke is applied.
Tip: In the layers panel, there is a target icon next to each path. Clicking that icon will select that path. You can also lock paths for more precise editing or select multiple paths at once.
Even though you no longer see the lines that separate the shade from the light, they are still there. Use the Live Paint Bucket tool to fill in the new regions you made.
Final Tip: Unfortunately, the eraser tool doesn't work well with live paint groups. To break apart a path more freely that might be closed off, created three nodes with the Pen tool, and then delete the middle node with Quick Selection tool. (Using the pen tool to delete a node will just change the curve of the line, not actually break it apart.
Let me know if you find this helpful. I've been exploring Illustrator for a while, and I know quite a lot about it. If there is something else you would want to learn, then let me know.