I think most would agree, the best way to find the "bottom" is in hindsight. (pun intended)
Most of the time I have tried to pick the bottom of any stock or Market, I'm wrong. It keeps falling. But if you wait until the chart shows some kind of obvious support level or upward reversal, you can probably get in at the right time.
Of course you will miss the very first profit from the very bottom, but you will get in much more safely. Why worry about missing the first 5 percent or so?