Drawings based on photographs often look awful - they're frequently distorted because of the camera lens or perspective, and details that look just fine in a photo can look strange or awkward in a drawing. To fix this, I use the Liquify filter in Adobe Photoshop, which allows me to smoosh the drawing around to my heart's content until everything looks "right" to me (#5). Then I add texts, background drawing and color to finish up (#6).
To make it easier to see how Liquifying works, I made a little animated gif that cycles between image #4 and #5. For anyone used to drawing comics the traditional way - with ink on paper - altering a drawing this way probably seems weirdly reversed, because it treats a "tight" ink drawing as though it was still "loose" pencils, making the end of the drawing process seem more like the beginning!
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(You can click on either illustration to see larger versions)