So far as I know, tipping is not generally done at trap events. At Maringo, we had the nicest young lady pulling/scoring/trapping for us on several events over three days, and I quietly slipped her a $20 after we finished our last round. That was an unusual circumstance, and I never mentioned it to the other guys on my squad.
At our local shoots the club members do the scoring, me among them, and occasionally someone will shake my hand and say "thanks". I always complement and thank the scorer, and the friends on my squad. On the way out, I thank the guys behind the desk and the folks in the kitchen at the host club for their hospitality ...especially if they're serving those wonderful dirty 'ol country ham sammitches.
For sporting clays, after a round of 50, we tip the trapper $5 each.