i know this is an old thread Dan but i have never heard of such a "trigger spot"...
i may just be lucky, but i used Michael Ellis' methods with the tug to teach my dog an out, i use the dutch word Los as his out command, but now no matter what he is holding i can tell him Los and he will immediately spit it out... i like to reward him with something else if i'm able to but sometimes i dont have a treat or toy handy and he has to just make do with praise and a pat... but he will spit ANYTHING on command, including edibles...