Tim to gush about topdressing and Milorganite!
Last fall, I core aerated and overseeded. I spread some Scotts starter fertilizer. The results were just "ok".
Last week, I slit seeded and topdressed with compost and peat moss. Then I spread some Milorganite. BAM! A week later, I have some major growth, particularly in the spots where I went over twice with the slit seeder:
If you are thinking of overseeding, definitely consider topdressing with compost and peat moss. The difference between this year and last is amazing.