Unfortunately, most holes where posts should go have to be drilled out with a slightly larger bit.
As I have gone through the same steps as you have, please refrain from drilling directly the through clearcoat layer regardless of the sharpness of the bit. It can and will happen that the clearcoat cracks or gets nicks in it. What I found very handy is putting the drill in reverse, and scrape off the clearcoat layer first. After you are through that, continue with the drill normally in forward.
Maybe try it first on a couple of holes that are out of sight or under the apron to get a feel of it.
I would install a cliffy at least in the NZ scoop, maybe a mylar between poppers and the right orbit where the ball exits the shooter habitrail. Another idea might be to install a makrolon playfield protector, if you can get it. These are very thin playfield-sized protectors that are placed over the playfield. We've installed a couple of these, and they are *very* nice.