I think you're mostly asking the wrong questions in terms of moving forward with your art. Any answers you get on here may be good things to try out but it's up to you which methods you're most comfortable with. You are in the right place though, this is a good thread to have in general.
Doesn't matter how long it takes. Take as long as you need to make something you're comfortable with calling finished. Could be 10 minutes, could be days, whatever.
Doesn't matter what program you use either. Anything that lets you draw in any way is fine. I even cut my teeth in Flash to begin with even though it's far from you'd consider an illustrating program. Try out as many programs as you want, it's all free to pirate.
Now, it can kind of matter what size it is though. The best advice I've ever received is to make a gigantic canvas (larger than 2000x2000) and sketch wth it fit to your screen. That way when you ink you can zoom all the way in till the one single line you want to draw next covers your whole screen. Do it in one long sweeping motion, undo, repeat, undo, repeat, etc. until you end up with one individual line that fits that part of your sketch. Zoom out periodically to see how it looks but you'll find you don't really need to very often.
But again, that's just me.
If you want the real answers to your questions I suggest just do art. Like every day if you can. http://artists.pixelovely.com/practice-tools/figure-drawing/ is going to be your best friend for that going forward. You'll settle into whatever methods you are most comfortable with naturally. You don't have to do anything the same way other people do it.