I was looking through Facebook and was reminded of this idea that after 10,000 hours of practice at any skill, one starts to get good at it. A quick Google found this: http://www.wisdomgroup.com/blog/10000-hours-of-practice/.
I suggest you all take a couple of minutes to read it.
Over my 30 years as a green woodworker, I must have made about 3,000 of these rattles, which take about 20-30 minutes each, so I would have a long way to go to get REALLY good at them!