What type of string/cord do people who successfuly thrum use? I have been
using cotton cord which breaks easily. Am I just being too rough or is
their a better material?
Depending on the diameter of cord you're looking for you might try kite
string or chalk line. Both are available at most hardware stores in
100-500 ft spools for under $3.00. Both withstand quite a bit of tension &
also resist abrasion better than most strings or twines.
I've never used them for thrumming, but that's what I'd try if I had to.
Good luck! Let us know how it works.