I grew up in the Pacific Northwest with wild blueberries and huckleberries. They like well-drained acid soil, and they come into disturbed areas (like after forest fires) where there is still duff on the ground. I think the bald cypress, while not found in the PNW, might be a good contributor here. I would mix in pine needles as well.
What I understood about the acid soil in the Northwest is that the ground cover (duff, composed of a lot of types of evergreen needles) is slow to break down, but as it does, the carbon dioxide generated from the slow breakdown makes carbonic acid (like in soda pop) and filters into the soil. I'm sure this is way simplified, and I suspect that there is a lot of material that would work to increase the acidity of the soil. Be sure the blueberries don't have wet feet. As much as they like a lot of moisture, they won't want to stand and rot in it.
I think rule of thumb to follow would be that whatever soil azaleas like, blueberries are also going to like.
_________________ Northwesterner
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