Ah, that explains it. Do you draw on paper first then upload to pc and paint it? I have an art pad that I have not used that much at all because I still don't get how to digital color my art that well.
Depends on what I'm drawing. I don't always do sketches if I'm comfortable drawing the subject. More typically, my digital art starts out traditionally, though--but it doesn't really matter, as long as the sketch is an image. I'm known to turn silly MS Paint doodles into something more by finishing them up in SAI, if I'm inspired enough. In a digital art environment, I do normally draw on top of a sketch or doodle to get started, yes. But, I'm probably a traditional artist at heart and probably am more efficient at finishing things traditionally.