I take a dread along with all the little stray hairs around it which fell out after sleeping on them, etc., then do some backcombing a bit more [if needed] with a teasing comb. I take the dread and do some palm rolling on it and twist it tight, and then I take my hot hairstraightener (enough to burn my fingers, but not my hair), and just fry the twisted dread a bit, and at the bottom too.
I find that it dries out the hair and somehow it sticks together better. I figure, the drier the chunk of hair is, the more tiny little broken hairs will be around and get all knotted and twisted easier. I've been doing it for a few weeks now and I've noticed a huge change in the thickness and overall appearance of my dreads, in that it has improved.
If you do decide to try this, lemme know how it works out for you. Leave a comment here, I get them emailed to me.