Here is a free pattern on this site

http://www.knittingonthenet.com/patterns/mittensthrummed.htm

I recently knit some thrummed bed socks. Haven't washed them yet to see how that will affect the thrumming.

Found this video on how to "thrum" when crocheting. Very interesting and instructions very clear.

Happy crocheting :)

Here is a link that might be useful: Video of how to do Crochet Thrums

Well, I learned something that I had not found in my previous research, and that is the last step in forming the thrum is completed by felting it between your fingers at the center of the thrum. That is new to me and I will use it next time.