Feeding 2 discs through the feeder slot and other feeding techniques

[Grim Tuesday]

At MSC this weekend, I watched someone (I think 469's) human player feed 2 discs through the feeder slot at once. While there is of course nothing illegal about this, I was under the impression this was very difficult and the slot was designed so this was not possible. How was he able to do it and why hasn't everyone been doing it all season?

On this vein, what are some techniques for feeding discs into robots through the slots that aren't readily obvious? I know a similar thread existed at the beginning of the season but everyone has had a whole lot more practice now and I think it warrants a fresh thread.