Finn was part of an elite unit consisting of four troopers, although his first engagement was what we saw in the film, he had been the most promising and had performed the best in training. It makes sense for Kylo Ren to remember the name of one of his best stormtroopers (who had come to his attention previously after disobeying orders to shoot unarmed miners who were on strike). <-- Extended lore, not from the film, but canon nonetheless.
As he was still a shiny, it is possible that he did do sanitation work in his spare time (his chore if you like), but he wouldn't have only worked there. It's actually a reference to the film Clerks by Kevin Smith, where the two lead characters have a conversation about Return of the Jedi and the destruction of the Death Star. The argument stems from the idea that since Stormtroopers wouldn’t be capable of doing something as trivial as installing a toilet that the Empire would be forced to hire outside contractors to do the job. This is most likely where the reference is from as Smith is a good friends of Abrams.
Since I don't like Ren as you do, I'd go with mind reading and device hidden inside of his mask. I've read a book about clone commando troopers and I think it could work simillarly.
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What are you talking about, he worked in sanitation