I'm not very clear on how Oekaki works either. I've managed to do some simple color-ins, but it is very hard to make anything decent with only a mouse. I'm sure all or most of the really great artists on there use tablets, though I've given to understand touch screens are becoming a viable alternative now.
Pretty much all of my work in Illustrator is done with the pen tool. I'm not even sure what half the other tools do because I've never used them.

The trick to using the pen is that you start with a crude, basic shape that looks nothing like what you want, then you use the anchors on the outline to bend and stretch it how you want. There are tons of tutorials out there if you're ever interested in learning, but it is an expensive program and I cannot advocate program piracy.