I would recommend sticking with LinkedIn.

Did you know that when using the Advanced Search on LinkedIn you can use a filter to only include people in Fortune 500 companies?

Set up a good profile page for everyone involved, make sure it has a photo.

Set up a company page, where you can also add a mini pitch.

Join Groups that contain your target market. You can send a message to group members.

Make connections, you need to expand your network to show up on their radar, as you can only see 1st, 2nd & 3rd
Join L.I.O.N & 500+ groups to speed this up

Don't Sell On The First Contact