Lyle,
I know you like your scripts, here's one to help with this tutorial. All you need to do is duplicate your layer as many times as you need and run the script to automatically align them.
CSS WebSprites contains three separate scripts the one you use is, Horizontal layers arrangement, side by side (hmagalhaes-layers-arrange-hor.scm). Vertical layers arrangement, one on top of the other (hmagalhaes-layers-arrange-vert.scm) might be handy to have as well. You'd only use, CSS file exporting (hmagalhaes-layers-export-css.scm) if you do web pages.
http://registry.gimp.org/node/25908