HI
How to send token to 500 people at the same time with one single transaction ?
When i look at in Myetherewallet.com there is no possibility to addmultiple address
U can't do massive payout via myetherewallet.
Try to find another ethereum wallet which supports multiple receiver sending.
Or
You need to develop a special ethereum script for doing this. But you need to be qualified in coding of such things.
If you can't then I can help you for $
I have experience in making such things as I am ethereum related web coder.