What’s the proper way to use wp_enqueue_script/style?

Do this at the head of your functions.php:

define('PATH_TO_URL', get_bloginfo('template_url') . [path to your libraries, etc.]);

Then, just call wp_enqueue_script('script', PATH_TO_URL . 'myscript.js'); or similar anywhere you want. If you change the location, just change the define() and it’ll update everywhere.

Easy peasy.