You didn't say where you're located, but for most of the US, now is not
the time to be seeding. I'd deal with the weeds, fertilize, adjust PH,
aerate, etc now. Then in early Sept I'd do the reseeding with a slice
seeder. Fall is the best time to seed, followed by early spring.
You're outside both those windows now, which means higher temps and
more weed competition, both of which make it difficult to establish new
seed.