I suppose you have a tool to run that many accounts. If not, you'll need one. Multiaccount Twitter tools support proxies. VPNs are not ideal for this task, because you need to manually disconnect and reconnect when switching between accounts and they're an overkill, because you don't need to encrypt your traffic, you only need to fake the ip address. Instead of VPNs, you'll need dedicated private proxies, which can be used on Twitter. Where do you find such proxies? Check out the Proxies for Sale section. When you have them, link each account with a proxy, 2-3 accs per proxy is ideal.