Where is your camp?

Is the grass in full sun (more than 6 hours a day) or filtered sun?

Does the grass get any water except rain?

You should have not top dressed it. I would have dug up the whole lawn, added the compost and dug it in, then replanted. If it has cracks that could be clay soil. Maybe the compost was not all organic, but had some clay in it, and then the compost decomposed and left you with clay. It would be better to buy a compost made of woods and other organics without any sand, clay (inorganics.) If you start to make your own compost, it will be the best you can get. Compost does not keep well and does not transport well. Supersoil brand used to have a good product in the 70s, but it got sold to Scotts, and now its terrible. For some reason since the 90s, you can buy good stuff in bags anymore. You may find passable compost, but not truly great in bags in nurseries. Clay soil means the water could be trapped and the lawn will not have drained properly. Thus the grass will be basically drowning. If you let clay soil dry out it turns rock hard, so you can't win with clay soil.

dchall_san_antonio - My camp is in Upstate NY and receives filtered sunlight throughout the day. It's primarily watered by rain, but I do water it a couple times a week.

tropical_thought - I'm certainly not claiming I am a professional. I initially tilled the whole lawn, then spread compost, then retilled again before planting. The ground was primarily composed of coarse grained dirt and stones, no topsoil to speak of. My intent was to bulk up what was already there with some organic matter, as it's only a camp and I'm not going to truck in topsoil. The compost I received was full organic and sifted from my local town that I further sifted and aged another couple of weeks before spreading, so I did put a little thought into what I was doing.

In light of what tropical thought said I wanted to reread to see if I could understand what he was talking about. I thought maybe I missed something, but I don't think I did. I'm not sure I agree with anything he said.

Bill, you said, "This year I got a load of compost and spread it over the lawn as a top-dress, but I'm relatively certain I overdid it. It's been on the lawn for the entire summer and while walking across the grass, which stays green but doesn't seem to ever grow - very weird I know - it's like walking on a layer of cork. No amount of watering seems to soften it up and it actually develops cracks in the surface when dry."

Reread what morph said up front. What you're experiencing is exactly why we always advise against rototilling compost into the soil to prepare for a lawn. Your grass will not perform the way you want it to until all that rototilled compost is completely decomposed. Compost needs air to decompose, and since it's buried, it doesn't get enough air to go very quickly. The shampoo will help in many ways.

Your original soil may not have been perfect, but it could have been improved more efficiently by 1) growing grass (or even weeds) in it, 2) fertilizing with organic fertilizer, and 3) soil test to correct chemical deficiencies or imbalances. The first two would get the proper organic matter into your soil and the third would improve the effectiveness of that organic matter.

The filtered sun is going to limit you to the fescue type grasses. Fescues quite often need to be overseeded in the fall, so is that going to be an issue?

Also watering twice a week is too much. Ideally you would be watering once a week when temps are in the 90s. When it cools into the 80s you should back off to once every 2 weeks. Each time it should be deep watered, meaning a full inch each time. That can take awhile to get it, but proper watering can transform a lawn.

The baby shampoo is effective in improving the drainage. Adding an equal amount of molasses may help with the breakdown of the surface compost you just applied. That compost does have the organic matter but it will take the worms a while to incorporate it into the soil at any depth. However, just because it is organic matter does not mean that it will provide the nutrients for the grass to grow as you may want it to grow. It will take a soil test to really know what nutrients are needed, however making several applications this fall with high nitrogen fertilizer at a 1# of N per M sq ft should get it growing pretty well. The cool season is when your grass likes to put on the growth and the nitrogen is necessary for that.

It would be good to know what the application rate was for the compost and what the product was. How many cu yds / M did you apply?