I was reading in "The Keepers of Light" that reticulation (in one of the processes being described) is caused by the Gelatin drying at a higher heat than its melting point (and being constrained from swelling/contracting where attached to base. I've never had reticulation because I tend to process everything at 68 or thereabouts.

But reticulation may add to the grain you are looking for. Taking the suggestion, then to cause reticulation, maybe it would work to put the film in very warm water, 135-degrees F or so, then dry it in a very warm chamber, 135-degrees or so.