For the 20s wait - try moving the printer 20s away from everyone. I put one in the far corner of the living room and by the time you walk to it it’s already done printing.
It's a good tip, though. But with mobile phones now, people tend to start printing already on their way to the room and then stare at the printer and wonder if it's OFF, starting up, pending, or if for some reason it decided whatever PDF they were printing was a bit too annoying to print (I do have occasional buffering issues with some of these printers, as I suspect their available memory/disk storage isn't great).