Baby bum wipes work a treat on everything. They cost nothing as well. They wont hurt a babys bum, but strong enough to remove the most stubborn yuk on any pinball.
I have used them on almost every machine I have in the fleet and it takes off mostly everything before i use the treasure cove kit.
When the baby bum wipes stop going brown, u know that all the grime is gone from the playfield before polishing.
* You can also get into hard to reach places with the bum wipes. Great for ramps and anything with the dreaded black fine dust stuck to it.
Give them a try, they work wonders.