Ibis Paint X. You import a picture from your gallery, Choose the recommended size, and then choose the Selection Layer. you use the bucket tool to fill in the spots where you want shadow. then, go back to layer one, and choose the Airbrush 40% tool(no ads needed for that brush). Make a quick spot(Make it the same color as your background) so you can put it on your most recently used brush list) Then go back to brushed and choose the Light Pale brush. (you will need to watch an ad for that brush) then use the Light Pale brush and make how big or small you would like. then put it on the place where you want the source of light to be. then go back to the Airbrush 40% tool. carefully put shading around the edges and places of natural shadow. then your done!
(ow my fingers)
