How to manually trigger flash?

[Sean Setters]

If you want to fire the flash five times in 20 s, it's quite simple: set the flash output manually and press the pilot button also five times.

If you haven't bought a flash yet, maybe an used 550EX could be good choice. It has stroboscopic capability, although the lowest frequency it's 1 Hz (as most of the flashes, I think).

Yep, this is a great answer. Basically, you're turning yourself into a programmable lightstand with remote trigger. As soon as you open the shutter, point the flash at different things and press the test fire button. Done.