How much did you use? I've used it as a shampoo almost every day for months on end with great results, although I only use a dime-sized amount and I add water with it.
No, just making sure that the hair is wet enough to distribute the smallest possible amount of soap. The trick is to figure out the minimum amount of soap you need to get all of your hair and scalp sudsy. I've used a shampoo-sized dose of Bronner's and had basically the same bad experience you described.
Hmmmmmmmmmmmmmmmmmmm, I think I used it like normal shampoo. To be fair, my hair would be decently oily by that point.