I struggle with this a bit. I wax my playfields (with Blitz). Perhaps it's my eyesight, and perhaps it's because these are home use machines that I'll hit up every few months, but it's really hard for me to see what is waxed and what needs cleaning. I feel like it's all pretty clean save some rubber dust.
What would be a simple test to determine there is enough wax on the surface, or if the wax should be replaced entirely?