Another interesting technique...

I got better results by swapping steps 3 and 5 (applying Watercolor first, then Underpainting). Note: There is no "step 4" as of this writing.

After applying the Watercolor and Underpainting filters, I used Edit > Fade > Watercolor and Edit > Fade > Underpainting to fine tune the effects.

I then used Noise > Dust & Scratches to soften the edges a bit and used a a Hue/Saturation adjustment layer for color enhancement.

Seems to work fairly well on landscape, floral-type pics; not at all well on faces.