If you wanted to experiment with distiller's grain, it would be a pure experiment. I believe it will work like magic as a fertilizer but if it works for weed seed suppression, I don't know.
The other product you mentioned, Secure 'N Safe, is an organic CGM product licensed for weed seed suppression. Here's a link.
http://www.grainprocessing.com/PDFs/secsafe1.pdf