I've written a dozen scans for bearinsh stocks ... they all sucked.
You made me look ... Here's a free site with a variety of Bear scans you can run ... I've never tried , nor will I, but if you find it of value please let the board know.
here's a simple "overbought with declining rsi" scan....i added a couple of minor tweaks for volume and price....brings up some good looking short candidates imo (charts below)
[type = stock] and [daily sma(20,daily volume) > 40000] and [today's rsi(14) < 70] and [yesterday's rsi(14) > 71] and [2 days ago rsi(14) > 72] and [3 days ago rsi(14) > 73] and [Close > 5] and [Volume >50000]