http://www.pro-mark.com/
Is this the preferred method over the adhesive "drop" method with the syringe?
"Preferred" is rather subjective, it all depends on who you ask.
My answer is yes, I prefer to use the rub on graphics but then again I am lazy.
The other thing to consider is that the adhesive drop method is going to give you a raised (3 dimensional) rivet, dry transfer rivets have virtually no thickness to them (not enough to be noticable with your finger anyway). Since most full scale aircraft built since the late 1930's have flush rivets, the graphics are probably more realistic.