I learned a new trick about managing skins. I didn't want to force any skins on my multiple blogs, and I didn't want the cookie to permanently take over either. So, in the back office, I disabled skin switching for all the blogs. Then I went through all the _main.php files (i.e. for each skin) and took out the conditional around the skin list code.

I removed this part:

if( ! $Blog->get('force_skin') ) { // if skin switching is enabled
...
}

When someone visits a blog, the default skin loads, but they can switch it if they want. They just have to do it every time they visit, or bookmark the url with their skin.