Also, check the condition of your window switches. Since the switch itself carries the full current of the window motor, a new set of window switches will work wonders. The switches are essentially the same as a Peugeot 504, so they are available if you don't mind the slightly different graphic on the switch.
On my SM the windows were vert slow and required a push both up and down , a check with the multi meter reveled very low voltage .
My solution was to fit twin relays in the back of the engine bay with the power supply coming directly from the battery and using the SM window switch to trigger the relays.
Windows mow move by themselves at an acceptable speed.