A rub n tug usually goes like so...
m: Feel good mai?
c: Yes thanks, are you nearly finished?
m: Yes, finish soon.
c: What about the elephant in the room?
m: Why you no tell me before?
m: What you like?
c: Happy ending thanks. How much?
m: (price)
c: Oh yeah!
At what point you approach the topic of a happy ending is up to you, though agreeing up front will save any disappointments.
If you're into massage then you also need to check out the soapy, the fishbowl and the Chinese ball massage.