SANDING AND PREPPING FOR CLEARCOAT
We need to sand the playfield to give some tooth for the clearcoat to stick to.
You mostly want some fine sandpaper for this job, maybe 800-1000 grit.
If you are clearing a reproduction playfield, or a new Stern playfield that has a clear coated surface, you can probably use 400-600 grit and REALLY give your clear some tooth.
On older non-clearcoated playfields, think of this job as de-glossing, rather than any actual sanding.
Don't press to hard, you don't want to sand off any paint.
Don't sand flaky paint that has turned to chalk. If it is chalky and dull, it will hopefully adhere to the clear due to it's lack of gloss. Many sys11 Williams games are just too fragile to sand.
You will probably have to hand sand with just sandpaper folded to get into cupped inserts and into holes and slots. Look at a reflected light source at an angle to see any glossy spots you missed.
Make sure you clean out the Shooter Lane and check how it will look with a rag soaked in Naphtha. You don't want to seal a bunch of dirt or grey wood under the clearcoat.
CUPPED INSERTS - I would sand these and fill them with clear from an eyedropper. You will see later why it is good to do this step before you clearcoat.
HOLES - Try and sand inside of slots and holes with emery sticks or coarse sandpaper (120-220 grit). You need the clear to REALLY hang on to these difficult edges. If anyone ever used Pledge or some other silicone based crap on the playfield, you will soon find out.
Blow out any holes on both the front and back of the playfield with your air compressor (do this outside, the playfield dust is toxic).
Wipe the whole playfield down with Naphtha, then follow with a Tack Cloth. Do not touch the playfield with your oily fingers or stir up any dust - you are ready to spray the clear.