Unfortunately, these hooks are usable out of the box.
attribute_edit.php is used by kernel/content/edit.php. edit.php does use the hook system, to add content actions. But the only way to re-use these hooks by yourself would be to write a minimalistic module+view, that loads the content module, adds the custom hook, and forwards the request to edit.
Right now I have a template file that overloads the edit_attribute.tpl file so that I can show the edit page specifically how I want it. However, what I need is to access an external database and set a template variable to decide which attributes will be shown (obviously all attributes are available on the backend, but depending on where you access this node you'll see different attributes). Unfortunately, I'm having trouble setting up code to hit one of the hooks in the edit process.
Ok, I see what you're saying, but I've never accessed an external db from the tpl files. I'm guessing is roughly the same as a typical template fetch operation?