Sorry, I'm about 2K miles from Vegas. But I'd bet that there is a local club that you can contact and join. That can be a boon to new users, not only for the experience, but for tons of other useful information too.
Beyond that, just try going slow enough to keep the threshold tone. Pay attention to the threshold breaks & nulls, and learn what they can tell you, along with the target tones/IDs. The idea is to isolate each target for identification, and to do that you need to GO SLOW. I'm talking 4-5sec/swing minimum....slower if necessary.
Sensitivity and swing speed kind of work together to maintain stable threshold. Excessive nulling means missed targets. If trash density is so high that you can't maintain a stable threshold swinging slow with sensitivity in the teens, then a smaller coil is definately in order.
Hope this helps.
HH