I tend to use the same technique for strands for braiding that I do for loaves of bread. It's a bit time consuming, especially if doing several 11 strand braided loaves.
Scale the dough and roll it into balls. Let those rest for at least 5 minutes to relax the gluten. Flatten them, fold the top down 2/3 of the way then the bottom up to the top. Fold the bottom to the top again and seal with your hand. Do that again. You should now have a log that is fairly uniform in diameter and can be easily lengthened.