There are many technical ways to describe a market reversal. Some can be RSI divergence, MACD Crossover or possibly MACD divergence, breakouts of key resistance levels or trend lines, etc. You can also use fibonacci levels which may confirm market reversals. But I personally didn't find to be quite in itself. I prefer to use these a reference in company with news and other information that would trigger a market reversal.
As with the put-call ratios, I do not have empirical data to support this hypothesis, but I personally think that derivative markets have there own characteristics (such as options markets are more sensitive to changes in volatility than in real stock price, people who buy puts doesn't necessarily hate the market but just to hedge, etc), which do not immediately reflect to the stock world. I have read a paper that used simulations to back the theory that given market efficiency and no-arbitrage, options markets are not more informationally efficient than the stock market.
In a paper I've read, it said: "In particular the model shows that one can use options' signals to predict actual stock returns when , by construction, options are infomationally irrevelant." ... "Taking these implications to real data reports surprising findings." ... "It shows that existing empirical proxies of informed options trading , such as the O/S volume ratio", "systematically fails to predict the difference between actual and synthetic stock return."
So, yeah, possible but hard. I would suggest you to combine technical analysis with real world news and economic data, and foundational analysis to form a complete view of the asset you are trading before you make decision on trading market reversals. For example to figure out if say the problem that caused the crash is over to establish a bottom line which it is not possible to exceed without black swan event, etc.
