I did not see where you included the warning not to drink hard alcohol here in Vietnam
. There is a lot adulterated stuff available. Many have been made seriously ill and died because of it. Do hope you will warn them. Good information you provide. Living here I see it all the time. But mush of it all you need to do is walk away. The cyclo driver the motorbike taxi, give them 20,000 vnd and walk away. A shave, 20,000 dong and walk away. That or like you advice get the price in advance thennegotiate to 1/3 of that, if that.