This is the BEST working way to invite all your friends to an event page. If you have another way please let us know and we will list it.
LAST VERIFIED WORKING : 4/7/15
Step 1 : Get Google Chrome
Step 2 : Get THIS ADD ON
Step 3 : Restart Chrome, Ensure the Add On Is Working.
Step 4 : Go to an event page you wish to invite your friends to and click on invite.
Step 5 : Click on "All Friends" to show all of your friends.
Step 6 : Click on the IFB Button on the top right (Shown Below)
UPDATE ON STEP 7 4/9/15 Of course 2 days after we post this it mysteriously starts working fine.
Step 7 : *IMPORTANT* Due to facebook's WAR ON PROMOTERS it seems like you can only invite successfully 500 people every time. Once it hits 450, click cancel so it stops (will take a second do not click anywhere else) and then it should be at 500; close the little box that pops up to spam you about the plugin and then click on send invites on the bottom right... Personally I wait 2 days between invites as overinviting can limit the # of people you can invite perminately however, do you. YOU HAVE BEEN WARNED.
Unfortunately, facebook changes their coding often and its hard to keep up with. However, we here at NYCR are in direct contact with this programmer and they have been on point.