Pretty sure Doremy's UL is the Kanashibari thing, due to the metal chains in her artwork, and for her Occult Attack, since the whole plot involves the Dream World, IMO, is just her trying to suck the dream versions into the dreamworld again.
If Sumireko is any indication in this game, you don't have to match your occult attack to your last world (Doppelganger vs. Lunar Capital Death Ray), Marisa's LW is a the most well known of the 7 Mysteries of the School, and Jo'on doesn't even bother to use an occult attack and just uses her sister.
Personally, I am amused by Yukari's decision to go with the whole Urban Legend thing. She's clearly enjoying this :V