Billy  

Went to the basement - billy popped.
Cleared games room twice and no billy.
Zoned in and billy instantly repopped with the games room PHs.
Cleared chapel 3 times.
Third time killed the named but didnt talk to the npc, zoned in and Billy popped on his own in the chapel.

Total only like 20 mins when whole of nek castle is grey.

trying to figure out how long it takes to make billy pop. so far 2 hours and i heard it was 8.