I just got finished taking the mylar off of my Earth Shaker (roughly same time frame as Tomcat). I got best results using rubbing alcohol and flour (took from vid's guide). Not sure about the Naptha, I'm planning on using it as the last step before I do my first clear coat.
To clean the playfield I used (from Home Depot) the Zep Citrus cleaner and also bought their blue micro cloths, worked well.