The short answer is, no. A hair dryer doesn't have the concentrated heat required to melt embossing powder, and the strong air will blow the embossing powder off of the stamped surface.

A purpose-built Heat Tool is the best way to emboss, and efficient too. Other alternatives (although not as efficient) are holding the paper over sources of heat such as a light bulb or the top of a toaster will also work.  Watch your fingers!