Some more digging on Google turned up a recipe for Natural Sourdough with Spent Beer Grains.
Used my levain from Ken Forkish's Flour, Water, Salt, Yeast to make the stiff levain. Followed the recipe, including the times, with the exception of reducing the water to 700g. My previous experience was that the spent grains added a lot more water and I wanted to be able to control the hydration. In this recipe the spent grains are added part way through the stretch and fold process. So I started out at a 70% hydration.
Once the spent grains were added, it was obvious that I had a wet dough, but decided to leave it and just add flour as needed when shaping before the final proof. On refection, perhaps I need to take 100g of spent grain, dry it out and figure the actual water content. The recipe calls for 250g of spent grains, so if the water content is at 50% then I'm adding another 125g of water for a final hydration of 82.5%.
Made two batches so that I would have four loaves, some to give away to the donor of the spent grains.
Proofed two loaves in bannetons, two in linen lined baskets. No apparent difference in the final proof. Not too happy with the minimal oven spring, but the final product is a hearty loaf, good crunchy crust, soft crumb. Here is the result: