I'm attempting to get precaching to work with cachemanager, but I can't seem to figure out how to enable the feature. I know most people recommend not doing this, but for the way we are using zenphoto it is must have. Current version is 1.4.5.2

You have to activate the plugin and set the options for your theme on the plugin options. If your theme uses custom sizes you might need to define those custom sizes on the themeoptions.php file.

Ok, maybe I am confused as to how precaching works. Will it automatically create the cache photos, or do I have to go into the admin panel and click the cache button?

You have to click on a button on the main admin page (overview). Otherwise the standard way of caching on request is still used.

Is there any way to have zenphoto do this automatically, or will I have to script that?

The automatic and standard way is the on the fly way caching when needed. If you need to precache - that why it is called "pre"caching - you have to do it manually.

Ok. Go figure. Thanks.

For your interest in case you haven't seen: http://www.zenphoto.org/news/caching