" Also I would like to reduce water usage and not having to top dress would be easier to keep moist. "

The other way around. Topdressing is easier to keep moist, actually, as it helps retain water under a layer. And the layer makes the seed moisture level more consistent.

But sure, you can do it without, if you like. Just make sure you're irrigating 2 to 3 times daily (or even 4) for a couple minutes to keep the seed moist. It may take a bit longer, but it'll grow. Been there, done that, got the T-shirt.

Farmers and ranchers around the world have been planting grass without topdressing for centuries. The important thing is to keep the seed in good contact with the soil. If you have a large area with no grass already, rent a roller for that. Otherwise you can walk it down. Walk on every inch.