Apparently you didn't read anything from this forum about seeding. Well, maybe you read others' opinions, but in my opinion, you have spent too much money to get to this point. I'm going to sound very negative at first. That is not to make you feel bad, but more to deter others following on what you don't need to do.

The bobcat is a nice tool for carrying stuff around, but it is not great for leveling the soil. I watched a video of a guy doing that last night - it was hilarious - like watching Laurel and Hardy trying to push a piano up the steps. The proper tool for a do-over like you did is a tractor with a box blade. That tool could have done in one pass what a bobcat might take all day to do. If you are paying by the hour, it makes a difference.

New topsoil is not a solution to old topsoil. Your new topsoil used to be someone elses old topsoil. You're simply trading your old issues for different issue. Old topsoil can almost always be restored to a very healthy condition with organic fertilizer.

The recommendation to aerate first, which I disagree with anyway, is so that you can drop seed down into the holes where it is supposed to sprout better. I don't get that, so at least you have not wasted your money on aerating.

Looking at the current situation, spread more seed to the thin areas, walk on it to ensure the seed is making good contact with the soil, and continue watering. When the new grass is 5 inches high, mow it back to 4 inches. You don't need more soil and don't need any hay. In fact hay is a serious problem for new grass. The product you were looking for was straw, not hay. Hay has weed seeds while straw does not.

All the water you need is about 5 to 10 minutes, two or three times a day. If your soil ever gets soggy, that's way too much water.

I would like to echo this, you can revive your soil.

My soil was dead when we got our house. Hard. Dead. You could just look at it and know it was dead. No signs of insects and it was like a rock. It was so super compacted and had pretty much everything wrong with it. The grass that was there had roots about an inch deep, and almost 1/2 of that was thatch. The only thing thriving was plantain and some seriously mature dandelions. Even the clover struggled, pretty sure that lawn had no fertilizer for at least the last decade. I pulled 5 full bluebins of dandelions in about 2500sqft, must have been nearly half the darn lawn. My soil was so compacted that even in a damp spring I bent and broke 2 steel weed pullers digging these weeds out.

I started reading a lot on this forum (and watched the many YouTube channels)

With healthy mowing techniques, and bringing in organic matter, my lawn is finally looking like it has a healthy environment to grow in. I started forcing life to the soil by topdressed with compost, filling in low spots with triple mix and using hen manure fertilizer. I have also aerated annually and have added 5 applications of baby shampoos (at 3oz/1000) this year which has dramatically improved my soils water retention and my root depth. What a difference.

By focusing on healthy soil, I feel like I'm finally going in the right direction. I am certain (after beating my head off the wall) that had I only added more topsoil instead of om, I would be absolutely no better off.

My point is, trust the advice of people here. They know their stuff.

I have also aerated annually and have added 5 applications of baby
shampoos (at 3oz/1000) this year which has dramatically improved my
soils water retention and my root depth.

In my opinion the shampoo did more good than the aeration. I need to keep a file of replies like this. It is amazing to me that people will refuse to spend 50 cents on shampoo to try this out. They prefer to hire a guy to aerate the lawn for $250. If you do choose to aerate, a good follow up would be the shampoo and flooding the holes with water. The whole idea is to improve the soil and water penetration.

Yup I have no desire to mechanically aerate anymore.

The kids that come around charged about $60 for 5000sqft. I can do 4 applications of baby shampoo on that 5000sqft for about $8 plus water.

I hope to do experiments with this next year now that I am a believer, but I think the shampoo is more efficient than anything. Mainly because I can keep the soil softer for longer due to multiple applications thoroughout the year, rather than the 1 aeration.

I basically didn't irrigate through the heat of the summer this year, and basically never got more than 1/2" of rain in any 2 week span. I did however shampoo once every 3 weeks through summer and the soil wasn't a rock like it normally is before a wet September.

I wish I would have found out about the shampoo a few years ago. Could have used that money on more organic fertilizer.

Baby shampoo? Really? How do you use it? Hadn't heard of this.

I use a hose end sprayer (ortho one), put in 3oz of baby shampoo multipled by the sqft I'm applying it too and blanket the lawn. I know dchall recommends watering it in after, but to be honest I have been lazy and haven't really committed to that.

I start off at a low setting and work my way up to flow rate that is suitable to my walking speed. Then you walk and spray (and pray). The amount of baby shampoo you added should be completely used by the time you covered your lawn.

YouTube gives you a rough idea as well: