Why does nose grease knock down the head on beer and soda?
Any oil should work. 

Naturally occurring surfactants, such as lecithin, make bubbles or foam because one end of the detergent molecule is hydrophilic while the opposing end is hydrophobic (not rabietic, though). Without oil, the hydrophobic end prefers air to water, encapsulating the air. With oil added, though, the water-repellent end is attracted to the oil, forming micelles, instead.

You could put vegetable oil or mineral oil on your finger, but then the server might wonder why you stick your finger in the beer.

You might also try making a beer-powered boat! Tell your server, and ask for a free beer to prove that this works.