Quoted from vid1900:

When a car wax says "wash car first", they are instructing you to rinse away grit and grime that could scratch your paint if it contaminated the wax application pad.
Novus2 is an abrasive. A fine grit that wears away some of your playfield, to "sand down" the surface of the playfield to the depth of the deepest scratches.
So Novus2 is not "cleaning" your playfield, it is grinding it down.
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Think if every time you cleaned your wood floor, you sanded it clean with very fine sandpaper.
It would certainly have the dirt removed from it's surface, but also it would not take too long until you sanded all the way through the clear finish to the wood below.
So I'm willing to bet you don't sand your wood floors every time you clean them.
You probably just vacuum to get any grit off and then wipe with a damp mop.
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Your pin is the same idea.
Vacuum up any dust or crud, wipe with a damp cloth, and wax for protection.
You don't need any fancy chemicals.
You don't need any fancy abrasives.
You don't need any fancy rituals.

Quoted from RobT:

The main objection to regular use of Novus 2 is the fact that it is a polish. All polishes are abrasive. Again: ALL POLISHES ARE ABRASIVE. That's how polish works.
So you don't need a polish to clean a playfield. You need a polish only if you want to remove fine swirls and scratches.
So to clean the playfield (remove dirt) you should use something that isn't abrasive (i.e., not a polish). Plenty of options, and I know people use Novus 1 for this purpose, but since it is designed for plastic, I don't. I use a cleaner that has polymers in it, which isn't abrasive, and it helps to maintain the integrity of your coat of wax:
http://www.autogeek.net/optimum-opti-clean-32.html
This product can also be used on the plastics.
You will never have to worry about using too much of this product. I wipe my playfield down with it pretty much any time that I have to remove the glass.