(minor spoilers) where to farm encounters in Waterfall?

[Nog]

Hey :) This is my first time doing a genocide run and I've just arrived at waterfall, and the kill count is on "18 left".
Where should I farm encounters? I've been walking around the checkpoint room and the waterfall area (the one with the echo flower and the camer) and I haven't gotten a single encounter.
(Please be specific about the rooms- some people say like "the room with the lamps" "the room before undyne" and ffs I don't remember in which exact room I faught Undyne)
thanks! :)

[taffyyy]

I usually farm in the darkening lanterns room

[casper]

I grind at the room before the turtle shoo

[Karma]

Originally posted by casper:

I grind at the room before the turtle shoo

you mean gerson's shop?