RE: Rattlin' Blackies
I am also new to the rattling of blacktail, (I have been calling bears for a dozen years) but I would imagine that in a small area you might only want to call/rattle for a couple minutes, wait about 15 minutes and then do it again. But I wouldn't call/rattle more than twice.
It is possible that the bucks are call shy, maybe they winded you or saw you. Maybe you rattled too hard, maybe they just aren't into it.
I have learned with bears that it depends on the individual animal. Some will run in, others will hang back and growl and others will flat out run away.