I'm brewing an Oak-Bourbon American Brown Ale today and I thought it would be cool to do a sour mash. I'm not attempting the sour mash THIS time, as I have not prepared it, but rather am considering using it on this recipe in the future. For this time, I was considering using Gypsum to give me an idea of what flavor I might get from doing the sour mash. Is this a good idea? How much should I use and at what time? Thanks for your help!