Martin,
I've had pretty good luck blocking the hammers just a hair away from letoff distance, then adjusting the letoff so that the hammers just wink when the keys are pressed.   It saves my back.  I imagine the magnetic strip would be a great solution for grands though.  You can get that at the local hardware store, then you could put tape on the back if you need to increase the thickness.  Full sheet labels from staples work well too. 
Respectfully, 
Chris Rawson, 
www.key-leveling.com
