Thanks for the link Bolty, I hadn't seen that one.
I have removed all the mylars (wasn't that fun
) and hit the playfields with a heap of Nifti, Orange Power Sticky Sport & Goo remover, and Novus 2. They look a lot better, but I still have a way to go to polish out the ball trails around the top loop and No Way Out entrance. There was a lot of really ground in muck, but it is slowy coming out.
I have sanded the underside of the mini playfield, and will do the same to the main playfield as they are covered in black dust / grime which seems to go everywhere. I haven't removed the pop bumper screws as I am worried that they will damage the artwork, so I will leave them in and just work around them.
Every little step I take forward is rewarding, the hardest bit is actually finding the time to sit down and do it!