This is easy,cheap,fun and looks great!
I use to do this to my dreads since I got my first one 3-4 years ago!
I used white embroidery floss,but I did some previous ones all colorful and they looked awesome!Ill post some pics of them later too.
If you dont have dreads,you could braid your hair and do the same.
Get your dread. :D
Cut a long piece of floss and tie it on your dread,the way that the knot is on the middle and the two pieces are the same length.
Wrap it around the dread a few times,like on the picture.
Cross it as many times as you like in an X pattern.
Wrap it again a few times.
Repeat this on other dreads as many times as you want.