Hi,
You ask the right questions.
Those white nylon knock downs are not user friendly and you will get better results using a steel bore knock down for normal highs and a rubber tip knock down for crowns. Check
www.ultradenttools.com for the rubber tipped one.
www.pdqtools.com for the steel bore.
Also, a small craftsman rubber/yellow plastic mallet works ok for crowns.
Try lots of light placement posistions to see the crown and pratice, you'll get it!
Jason the Dent Medic