I was recently asked to do a cover for the Marvel comic Lockjaw and the Pet Avengers. Here's a step-by-step snapshot of the various stages, because I've recently been asked about such things.
First I did a couple of roughs...
The one selected for developing into a fully-rendered cover was the second one, so I then drew it in pencil on a piece of letter-sized paper.
Finally, I scanned the pencils and blew them up to finished art size, printed them out as a blueline (light blue lines which can be inked without reproducing, so only the inked lines are visible), and inked everything with a No 2 sable brush and a Hunt 102 dip pen.
Ta-dah! Wyatt Wingfoot's your uncle.