Try the Cinnamin Bark powder. I t works pretty good, and with a lot that size, you can stay on top of it.
I personally would tear up, that one section that is nothing but CG, and keep it clean until seeding time.
Whatever you do... don't let it go to seed...
Now that I know that clay's texture(platelets) has nothing to do with water infiltration, percolation, or drainage,,, I wonder what does...