There are lots of circuits on th'tinterweb using a 555 timer or similar to act as a servo tester.
It needs two of such, one to set the servo to "this way" and the other set for "that way". Connect the servo signal lead to them via a really cheap slide switch so that it gets one signal or the other. Or use two testers and switches. I can't really think of a simpler way of doing it, or, given the price of point motors and their switchgear, a simpler way. Two circuits for the entire layout, one cheap slide switch per point.