To encourage felting people use hot water (smetimes alternating very hot and very cold) agitation and soap. The soap of choice isn't a soap, it's a detergant.
I know we have all been told to aviod detergents at all costs. the way detergents work is by breaking oil down really small and lets water rinse them away. I actualy use Dawn once every two months. everytime I use it my dreads feel INSTANTLY tighter. you know how your clothes shirk in the wash when using detergent? Same principle. This will make the parts of your hair that are already dreaded tighter. it won;t really help you with the half inch of loose hair near your scalp. DO NOT TRY THIS WITH NEW DREADS!!!! it is of my opinion that it probably won't help.
This is not to be done frequently. I have used dawn once this year. I use it whenever my hair feels fluffy and shiny. I know of no actualy reason that you shouldn't do this frequently, but my personal feeling is that it is very powerfull and with great dreading power comes great dreading responsibility.
I use a very small amount and rince for about 5 minutes afterwards with hot water. then I rince with cold wter for as long as I can stand it. Then I wash my hair with my normal soap and rince the same way. after I use the cold water I go back to hot water and rince until I smell no more lemon. the nice thing aboiut lemon scented is that ou can smell it if it's still there.
If this doesn't sound right for you don't try it. You can't say it's a bad idea unless you have personaly tried it. If you do decide to try this ut let me know and tell bme how it went. I am the only person I know of that has used this method.