OK, basically, since it is pretty much impossible to backcomb them (cuz you'd have nothing to hang on to), you have to get them to dread more or less on their own. The best thing to do is to be constantly rubbing the tips between your fingers. Y'know, when watching the tube, reading, etc. Just keep rolling the tips between your fingers, back and forth, knotting them up a little more each time. Some kids have said that it helps to put a little of the wax in the palm of your hand and then take the dread tip and rub it around in the wax until it gets all frizzy and blunt. Don't be shy to use the wax, heck, that's what it's for! And again, don't stress about the loose tips either, everyone with dreads has them. And if you like, once you've had your dreads for a year or two you'll be able to snip off the undreaded part and your dread won't come unraveled.

Knotty Brianna:

"My tips were very undreaded for a long time. One day I started taking the tips, half in each hand, and gently but firmly pulled them in opposite directions, alternating different chunks of my tips. You can even hold/pull the majority of your tip down, and pull small pieces of the tip upwards at the same time, taking different pieces as you go. This seemed to really work and if you spend like 5 minutes on each dread in your spare time, you can really knot them up this way! I began doing this at about 7 months."

Also, Shrimphead had something to say about keeping those tips dreaded:

"I had dreads many, many years ago. And last week I decided I wanted them back. I got your dread wax and I love it. Thanks so much! Now to the tip,(pun intended). My wife wanted the ends to look 'finished' and not wispy. So she hauled out her felting needles and started at them. It sounds weird. But dreads are really just felted hair so she figured that she could just needle felt the ends. And voilá it worked like a charm.
So if you want good round ends try felting needles."

Thanks so much Knotty Shrimphead!!!