Here´s a little behind the scenes work from the New Mutants cover 25.
I first did the 3 sketches and I sent them to the editors. I usually do all this process digitally on a cintiq.
Once the editors pick one of the layouts I start working on the finish pencils. I usually do a printout of the layout and do a trace over on the light table for the clean pencils.
Then I go to photoshop to apply colors till I get the final render.