Yep that's exactly how I was taught to do it and it works very well. I put small cheap hygrometers in each jar, and put the buds in when the smaller branches snap. I don't wait for main branches to snap this takes too long. Once in the jars, I monitor the humidity: when it's more than 80% I open them for a day and/or take out the bud; more than 70% i open the jars for a few hours; 60-70% for 30 minutes or so. just keep doing this until the humidity stabilizes. Which is normally after about 3 weeks with me.
You can order these from www.amazon.de: http://www.amazon.de/Mini-Hygrometer-analog-rund-Durchmesser/dp/B00358RRMI/ref=sr_1_9?s=garden&ie=UTF8&qid=1379338520&sr=1-9&keywords=hygrometer
I use these but they are only accurate to within 5-10%: http://www.amazon.de/Exo-Terra-PT2466-Hygrometer-Rept-O-Meter/dp/B00026053Y/ref=pd_sim_sbs_hg_2
They will deliver to the Netherlands.