How to play Jhin in URF
Take this build:

By the end of the game you will have over 500AD (with elixer) and 90%Crit. On top of that with every landed w and crit you go from 500ms to ~970ms. (I tried this in practice tool and in normal game it drops down to ~650 per crit. It is a really fun build and is "sorta" viable.
I will admit, at the end of the game 1 person called me a troll. But you know what, URF is meant to be a fun gamemode. And I had fun, My team sort of had fun (i say sort of because only 1 person really talked ALL game. And he was laughing.) The enemy team was dying of laughter and happiness as they made a comeback because the game lasted too long (cause i was farming.) But in the end, most of the people had fun with this inventive build.
BTW im not the person that came up with this. I saw it in a YT video.