Clear coating a playfield only is pretty easy. The skill is on playfields that require airbrushing, touchups and repairs. Then it's sealed in with clear coating.
Any of your REAL playfield restoration companies, like HSA Pinball, Playfield Renovations or Bill Davis will tell you that MOST of our business is on playfields that require repairs/airbrushing and very little of our business is just the easy clear coat only jobs. Even NOS playfields require mylar removal, drilling, and some basic touchups before doing the clear coating.
If DC2010 wants to get in the business of playfield restoration then more power to him. It's a lot more work than he thinks. Send him your ES (Earthshaker NOS) playfield and see if he can handle the special steps REQUIRED to clear coat on sys11 playfields.
Here are some pictures of what a playfield restoration is:
http://www.hsapinball.com/HSA_PINBALL/Restorations_Examples/Restorations_Examples.html