i wrote this plugin a while back for a client and never got around to polishing it off for general release.
https://github.com/dwenaus/bp-rate-vote-like-anything
Myself and another developer plan to launch it soon. But even as it is now, it’s totally solid and very cleanly coded. I wrote it because GD Star Rating plugin was so bloated. Basically it provides a framework for you to rate or vote or like any wordpress object that has a db id – so yes a custom post type is no problem.
UPDATE: I’ve made the repo private until I release the plugin.