A power window switch as you say is a momentary contact switch; it toggles a 12V pulse pushing one way and a ground pulse pushing the other. The cleanest way to use this switch to control a device is by using a 12V solid-state automotive latching relay. This latching relay is wired so that the 12V pulse "closes" the latching relay load contacts, energizing the device. The relay will stay latched until you push the window switch the other way, send a ground pulse that causes it to change state and opens the contacts disconnecting the device. It can work for any load device (lights, winch control, etc.) providing the latching relay load contacts are rated high enough to handle the amp load of the device.
THIS is an example of an automotive latching relay. Industrial supply houses like McMaster-Carr or Grainger also carry these relays.