Important--the iron never ever rests on the yarn. The you-tube shows 100% WOOL yarn, and for woolen yarn, you can sorta-kinda-almost touch the yarn with the iron, as shown. For non-woolen yarn, and particularly for ACRYLIC yarn, do NOT come as close to the yarn as shown in the you-tube, instead, keep the iron about an inch or so ABOVE the yarn, or you will over-steam the acrylic yarn into a rather limp state (over-steaming, alarmingly enough, is called "killing" the acrylic!)
For verrry stubborn kinks, where steam-de-kinking does not work, you can go back to the 2007 post and have a look at how to de-kink yarn the old-fashioned way, by wet-blocking, but do try this instant-steam method first!
Good knitting, TK