I don't know why anyone hasn't replied to this post yet as I have seen a few clearcoat playfield threads so those guys must know. I may be facing this same question soon when I start on my playfield. I have been wondering like you do I leave srcews, posts etc in the playfield so the hole is still there after clear coating. I thought if the hole is filled by a clear coat, does inserting a pin into whats left of the hole somehow damage the coating? Hopefully someone who has done a playfield will chime in with an answer.
