Blowing on the call and making a prey distress sound is actually the easiest part of the whole ordeal.
Believe it or not, if you're calling in undisturbed "fresh" areas (where the yotes haven't heard every Tom, Dick and Harrys' rendition of wascally wabbit in pain); then the sound makes little difference.......If you blow it they will come.
Being successful is alot more about our approach to the set, setting up in a place we can see them coming, being mindful of wind direction and how our scent is being distributed, being mindful of where the coyotes probably are and where they will likely come from, keeping our movement to a minimum, our un-natural noises quiet and our outlines broken by cover. Additionally; how we handle the approaching coyote/coyotes and finally, making our shots count.
Remember, every coyote that gets away alive (especially if missed or wounded) will be educated and may not respond to that type of sound again for quite some time. I've even seen the adult coyotes teach their pups not to respond to a particular sound. Anyone who calls coyotes will educate some, but the idea is to keep that number down to the absolute bare minimum. Most of us don't have unlimited acres of virgin places to call these days, and all the newbies (no offense meant) have managed to educate a boatload of coyotes for us.
Best of luck.