Best Bulk People Finder/Info/Locating Service?

[Account Closed]

I work for a handful of investors. Every month, I am handed a list of sometimes 100+ properties, 200+ properties, et cetera. I finish one list, they hand me 2 more. It's never ending. Obviously, my job, as their licensed broker, is to track down the owners and see if they are willing to sell. If it's on their list, they'll buy, no questions asked. So, it makes financial sense for me to indulge these requests.

However, I need to prioritize my time, as efficiently as possible. Googling one owner at-a-time, FB'ing them, tracking them down on LinkedIn, et al, is a mind-numbing task, with some owners taking days to track down to some small village outside Tokyo (actual example), or staying awake until 3AM so that I may possibly catch the owner right before their lunch break, halfway across the globe. As the lists begin to grow larger, I am finding it would be a more effective use of my time if I were to outsource this data find. All lists come complete with property address + owner's name. I just need contact info.

Any of you have any experience with bulk, owner locating services? If so, might you be willing to share which services you've used with success? All I need is a phone #, or an email addy.

I've read some of you have used privateye.com (peoplefinders.com), as well as findtheseller.com, amongst a small list of other sites.

Any, and all, information you may share would be greatly appreciated.