Targeted sharedrop is the most effective if you wish to real in the cost involved in sharedropping.
In other words, drop on those who really do want to use/support the system that take an action to claim their shares.
This will allow you to cherry pick active members who actually care at all about your project and keep your balance sheet from not looking like total crap afterwards.
Lets call this.. 'smartdropping'
Yes.. BTS would make the most sense. Smartdrop on BTS.
Given that it's a targeted approach it might even allow you to increase the % points for further incentive.
DISCLAIMER: I have explored the idea of sharedropping numerous times.. after tons of conversations both with people who have done it and people who have been on the receiving end of it.. I am not a fan because I think the desired results by the dropper are far from expectations. If you are going to do it.. I recommend smartdrop like I said.. however I think you would be equally be happy just with an email subscribe list.. and save yourself a lot of programming time and headaches.