Quoted from vid1900:I would wax first, then put Mylar over any common wear spots, or areas that are starting to wear.
Once the wear starts, it keeps growing, no matter how often you clean or replace balls - believe me.
I really dont see anything wrong with putting Mylar on a playfield that is on its way to getting trashed if you dont do something to it? I put mylar on my Firepower playfield because it had a few spots that was all the way through the paint and into the wood. It plays just fine and now I dont have to worry about the playfield getting totally trashed.