The lab of UC Berkeley scientist, Noam Sobel, found when examining the "Influence of Smelling Coffee on Olfactory Habituation":
Smelling coffee aroma between perfume samples, as compared to smelling unscented air, actually works. The perceived odor intensity of the perfume from sample to sample stayed the same after smelling coffee aroma while it decreased when smelling air between samples. The pleasantness of the perfume, however, was similar after smelling coffee or air.
This isn't the only way to clear the nose and increase sensitivity for the next evaluation. Other popular nose-clearing techniques employ smelling a swatch of wool or smelling an unfragranced forearm. Now go forth and impress your pals about the coffee beans at perfume counters nationwide . . . and it helps to toss in "olfactory habituation" a few times while you're at it.