There are a few indispensable resources that can greatly improve your mastery of Photoshop in production.
Adobe Photoshop Restoration and Retouching, Third Edition, by Katrin Eismann and Wayne Palmer (New Riders Press, 2006)
Photoshop LAB Color: The Canyon Conundrum and Other Adventures in the Most Powerful Colorspace, by Dan Margulis (Peachpit Press, 2005)
Photoshop Masking and Compositing, by Katrin Eismann (New Riders Press, 2004)
Professional Photoshop: The Classic Guide to Color Correction, Fifth Edition, by Dan Margulis (Peachpit Press, 2006)
Real World Color Management, Second Edition, by Bruce Fraser, Chris Murphy and Fred Bunting (Peachpit Press, 2004)
Photoshop Studio with Bert Monroy: Digital Painting, by Bert ...