how do you mean?
Instead of trying to profit from the <5% fluctuations that happen in the span of a few days, trade on large time-scales; ie. buy now and sell when the price is at 800$, then buy back at 600$, etc. This is less risky, since it depends less on luck.
I think that's what he meant.
It's all about opportunism. Set low buy orders, high sell orders - you never know if they are going to be filled, but if they are then you're laughing.
Flash dumps occur more frequently than you might be inclined to think - if you're one of the smart ones with a speculatively low buy order then you can profit massively if/when the dump hits the market you're trading in. I don't mean a few hundred dollars, or even over a timescale, the returns can be massive - many thousands from a few hundred, and almost instant by dumping in another market or exchange.