If you're over-seeding, you have to keep the seed watered every day until it sprouts (about 5-6 days) and then every couple of days until it gets growing good. It's probably too late this year to over-seed as the ground is starting to cool a bit too much. DH also puts down gypsum every couple of years because we have easily compacted fine stuff on top of clay. If you're not over-seeding, no additional work is required after aerating and fertilizing.
