My REAL issue with spray or horns for barking in crates is that I worked SOOOOOOO hard to make the crate a positive thing (it was not at first) and I wondered if Bear would eventually not want to go in the crate being the softie he is.
We taught leave it using a jackpot game. I heald a treat in my hand, he's sniff and paw, the minute he redirected his attention to me or looked away from my hand, I rewarded so leave it came to mean leave that tempting thing and look at me. check this site for more detailed instructions
ClickerSolutions Training Articles -- Teaching "Leave It"
As for teaching a dog to come after "leaving it" if you have a clicker trained dog (and click ends the behaviour) once you click for reorienting to you good behaviour - he is coming to you for his reward. Same goes for ALWAYS pairing a marker word (like yes) with a treat. You start close and move out, Eventually you say leave it and he comes to you because he can put 2& 2 together and , like chili knows that leave it = PARTY!