I thought you meant buying perodically during the crash. Because this article is about crashes. Most people who make money buy and hold. But the times of crashes can be another opportunity.

You should check out the buyer and seller bars very carefully. If red bars are way more and huge, you can know that the crash is not over. So if you do the research well there, you will make some extra profit. The more you are better analyzing charts, you can predict some stuff.

Search for "Quants". They run the Wall Street and they're mathematicians who see different stories in those charts.