http://www.graphic-design.com/Photos...tch/index.html
Backing out of this URL to the main photoshop page will take you to many other useful tips in tutorials.
http://www.graphic-design.com/Photoshop/index.html
And for another tutorial for an ultra-realistic watercoloring method for photography, look at the second page of the sketch tutorial for the following paragraph near the bottom of the page and click on the linked text: "15MB PDF Format":
"MORE:
Download Tim Shelbourne's Watercolor Effects from the Photoshop Photo Effects Cookbook - 61 Easy-to-Follow Recipes for Digital Photographers, Designers, and Artists 15 MB PDF Format)"