That's what he means.. scan and redraw in PS with pen tool.
Having a tablet is the easiest ticket in doing it. But doesn't mean you can't do it the long way....
Do your drawing on paper making sure to clean out smudges or dirty areas and make sure the lines are dark. Scan them and open in PS or , even better, in Illustrator where you can create vector shapes..
In Photoshop, you need to abstract the grayscale line drawing pixels from the white background and assign on a layer. This will make coloring easier. If during the coloring process, gray pixels or discoloration appears in the the color areas, this is caused by almost invisible gray pixels in the line drawing layer.
Convert the image to grayscale, use the brightness/contrast controls to adjust darkness and brightness of drawing, This is to get the blackest black in the drawing and whitest white of the background. Why do this? This will ensure that you minimize any stray gray pixels in the supposedly empty background not needed in drawing.
CTRL+click the grayscale channel icon in the channel palette (this will select the white areas) . Inverse the selection and on a new layer, fill the selection black. Delete or Hide the original drawing layer for future use. Do not flatten and SAVE. The new layer is your original version drawing.
CTRL+click the drawing layer icon, this selects the entire drawing, hide the layer. In the Paths pallete, create a work path from the selection.
You can use either - FREEFORM, CONVERT, ADD, and DELETE pen tools - to adjust the shape of the work paths anywhere you wish.
If during the whole process, you accidentally deselect the paths or it disappears, just click the work path icon.
When done doing the edit, CTRL+click the work path icon to bring out the marching ants selection and in a new layer, fill with black to see the new drawing.
If not satisfied, hide or delete the layer , go back to the paths tab, click the work path icon and continue the edit.
I don't use Illustrator for this, I'd use Corel Draw to do this stuff but not everyone has Corel Draw,,,, . But If you have Illustrator, its best to use it for better vector results.