Insider buying can be an excellent indicator of how well a spinoff will perform. Because spinoff stocks are newly issued securities, if insiders are buying stock in a spinoff, its probbaly because they are confident in its performance. Insiders know a company better than anyone, so when insiders are confident about a major corporate event, such as a spinoff, it's a very good sign.
I gathered data on the spinoffs within the last 10 years that had insider buys within a few days of the spinoff date, and sure enough the results were what I expected:
As you can see, all but one spinoff stocks that had insider buying outperformed the S&P 500. Pretty reliable indicator, if you ask me...