I am exploring the best way to do this yet.
I am thinking I would pay by the share similar to signature campaign, unless somebody offers shares in bulk. My only concern is that i would want shares for legitimate traffic, not just for appearances. Please let me know if you can help me!
What's the page about? Bitcoin related?
The best way is making a advertise on facebook a.k.a paying to Mark... For sure you will have a better reach and you can choose your public too.
Or well, you can try to pay bitcointalk users to share however they can delete the post after received or something like that... Maybe you can pay to advertise in a group(fixed topic, cover photo, ...)