Berkshire Hathaway Inc (BRK.B)

[gfp927z]

From a TA/chart perspective, BRK's chart actually looks better than the S+P's right now. During the Dec lows, BRK held at its summer 2018 lows, whereas the S+P plunged much further, all the way down to levels from early 2017. Breaking trendline support (both did) isn't as important as holding the other support levels. Usually trendline support is merely the first support level to fail.

The bigger potential problem for the broader stock market is the growing possibility of a bearish Head + Shoulders forming. A recession will come at some point, the 10 year old bull market can't last forever.

Instead of using charts, the main metric Buffett uses is market valuation, as measured by his ability to find good values/cheap stocks.
That's a much better metric to use if your goal is to buy undervalued stocks and hold them long term. The chart might be used as a 'screen' to narrow down the stock candidates, but then the fundamental analysis of the stock begins. On the other hand, using charts/TA is better for short term trading.