I remember reading that there was a way to modify the rocker switch which disabled the the return spring. The downside was that you had to manually stop the motor by manually returning the switch to the center position . . . far from optimum.

There are kits that convert existing power windows to "one touch" up & down. They also have a safety feature which stops the motor if there's an obstruction, such as fingers. Typically, the units only convert a pair of windows, so if you want to do four windows, you'll need to buy a pair.