1 is the bottom apron. How do you clean these things , I have tried on other gottlieb games and the paint/print /what ever it is just wipes off...Is there a secret

You DON'T clean them, that is the secret 
I think ANY kind of cleaner will remove the print on these things. I'm not 100% sure but i think these things are silk screened with ink and it pretty much just wipes off if any attempt to clean them is made. If it is in shitty condition, you're much better off to repaint and use a Pinball Rescue decal  I will be doing that on your Solar City apron as its scratched