I did get a bit lucky in rain timing and amounts the first few weeks. I'm convinced the secret in my area on clay is: doing a heavy lime application, moderately heavy fertilizer application (12-12-12), light disc pass, spread grass or clover, light drag to set seed then oats or rye drilled in. It is a bit of a process, but I've always had good results. To me, the possible excess nutrients from fertilizer are less worrisome as a washout and bare dirt problems for no ground cover. When I've gotten lazy and didn't do all the steps my cover hasn't been nearly as good.
