Additionally, my compadre Scott Kurtz of PvP taught me another nice Photoshop technique on our "Webcomics Weekly" podcast this week: Essentially, it's a low-level, single-color transparency layer that gives the whole strip a cohesive feel. It's as though you're looking at a full-color photo, but viewed through a soft-yellow plastic transparency sheet.
A doff of the cap to both cartoonists for the techniques: It'll be fun to experiment with both in the weeks ahead. Hope you liked 'em!