San can be added after almost anything. Waiter-san, grandfather-san, Canada man-san (Canadajin).
Gaijin is a way of saying foreigner. It is actually kind of a bad word, kind of like gringo is in spanish, or kind of like cracker to a white guy in english. It's not a very good thing to say, but most Japanese people (Nihonjin) don't understand that if they say Gaijin-san, even though san is polite, it doesn't make gaijin polite. It's kind of like calling someone a jerk, if you say Mr. Jerk, it doesn't really make it any more polite or and less rude. But, they don't realize that. I just thought it was interesting.