Every person takes different tactics, some can be swayed by just telling them it's a fun game of grabass, others will do it for cash. Of the friends that didn't take money to sway, some version of "No I swear, it's really fun, let me show you...". I don't hide it's a kink thing, but I make it as casual as possible during the actual sesh. Even when they don't "like it" in the end, it's never ended badly.
Now with dates, I just up and say it gets me off, and I'd like to see if I could get them into it as well.