I've tidied up the post and linked the Youtube videos for you Hans 

I spent some time watching all these videos a while ago, and both restorers have been gracious enough to share their methods and experiences. Youtube has a lot of info in playfield restoration and they are good starting points to develop your own methods.

There are AP members that can match and surpass these methods, and I've seen "first hand" some of the results and they are quite staggering. Going back 10 years ago, no-one was doing this kind of work, and it is great to see the exposure of the methods on youtube !