1. Right click anywhere on the page and click "Inspect element"
2. Click the Network tab
3. Vote the first time (on the page)
4. Look for an element that says vote_json in the list under the network tab (you may have to scroll down)
5. Right click vote_json
6. Click "Replay XHR"
7. Go to step 5

EDIT: for windows users, you can press the "menu" key (not present on some keyboards; if it's there, it'll be between the alt and control keys on the right side of the keyboard) and then press R when vote_json is highlighted. Do this a bunch of times in rapid succession to vote again and again.