The blue Primos calls are sure easy to use, but sometimes lack the emotion needed to get bulls to come in close. Now with that being said, Im sure there will be some guys chime in on how it worked great to call in their big bulls, and thats awesome! But, many times in areas that get a lot of hunting pressure, that call lacks some of the realism that diaphragm calls can make.
For me, the Bugling Bull elk calls work best. Hear is a link with tons of FREE Youtube instructional basics. https://www.youtube.com/channel/UCRyJ7SpQNrFuykjEOHtPyJw
For more in depth calling and elk hunting tactics, get the University of Elk hunting video by Corey Jacobsen, sold here in the Elk101 store.