I've just had the lawn core aerated by a service; today I'll top dress with 1/4" Leafgro compost, then overseed with Tall Fescue and fertilize and lightly rake the seed in. I had thought it was advisable to only lightly water the seed each day during the first week or so until it germinates. But the service that aerated my lawn says "one good soaking to wash seed in and establish good soil moisture, 1-3 hours per area." (Then they do say light watering each day after that.) What do people here advise on how much to water right after overseeding? I live in a Maryland suburb of Washington, DC. We had half an inch of rain two days ago, and nothing forecast for this week. Thanks.
You just need to keep the seed moist. Unfortunately that means that if the air is dry that you will need to water frequently. 2-3 times a day maybe. If you have a top dressing of peat you might be able to get away with less frequent watering.
You'll have to keep that up until the seed germinates, then you can start watering less often, but more deeply. You want to train the roots to go deep for water.