I frequently use a 3rd party designer to help with the tedious task of going from PSD to final theme. If you haven't realized it yet, but alot of designers have problems setting up a local MAMP install w/ drupal in which to fuck with css. To deal with this without giving the designer any command-line access, my shop uses what we call CZI on all drupal installs. This stands for CSS Injector, Zen theme, IMCE, and allows a designer to upload images and apply css rules to a development site they have been given permissions for on the theme, Zen, that provides all the classes and ids anyone would need.
After my shop, the designer, and the client are satisfied, CSS Injector and it's external files become a weight and need to be removed. Below I detail the process of using Zenophile (http://drupal.org/project/zenophile) to create a zen subtheme in which to wrap up all your CSS Injector files: