Water daily for a week then kill everything with RoundUp. Continue watering daily for another week to sprout more weeds and spray RoundUp again. Scalp, clean up the dead weeds and seed.

After spreading down seed, immediately spray Tenacity and water in, it will stop a lot of weeds from germinating along with the grass.

Once established, get on a prodiamine pre-emergent program as explained here and keep that going every year. Spring application time around here is around March 1st.

For hard soil you can use Morpheus Soil Conditioner or baby shampoo at 3oz per thousand square feet.