How tuned up was your lawn to begin with? You said it was thick. Most fescue lawns would not be described as thick, or dense, without some fairly intensive attention to achieving that goal. On the other hand, if you have a Kentucky bluegrass lawn, there is nothing you can do to stop it from becoming thick. If you know you have KBG, then you can sit back and watch it return. If you had fescue, then it will not return until you get more seed down.

Do you have full sun or is there more than a few hours of shade on the lawn? KBG will not grow in the shade at all.

What will the lawn be used for this year? Are you planning a volleyball party or anything that will dig it up or slog it down?

Aeration: Whew! Someone on another topic challenged my wisdom on that subject. Well, first of all it is not my wisdom. I learned it from reading and listening to people smarter than myself. Then I tried it and it worked exactly as advertised. The more I read the less important I think mechanical (core) aeration is to the homeowner. The research in this area comes from golf courses. Here is the executive summary. 1) Organic matter on a golf course is considered a pollutant because it clogs the pores of a sand soil. 2) Core aeration of the playing field opens up large holes in the soil and helps to allow water through the clog. End of summary. The important things about their use of core aeration are that it is a sand soil and the grass is mowed every day. Normally sand is extremely porous and allows water in. In the golf course situation with continual mowing, they develop a layer of mowed grass particles which seal off the sand. Furthermore, decomposition of the golf course grass results in a waxy byproduct from the microbes in that environment. Core aeration works to open their soil to water. Another solution found to work for golf courses is to spray them with a surfactant. Surfactants release the surface tension of water allowing it to penetrate wax, oil, and clogged soil. Another name for surfactants is soap or detergents. They come in all varieties and some may be more effective than others. However, I have found that generic baby shampoo from Wal-Mart works fine to soften hard soil. Apply at 3 ounces per 1,000 square feet two times. Apply once and water an inch after the soap. Then the next time you water, don't use the soap. The second time you water, repeat the soap. That is all.

Whether you apply some seed now is up to you. There are going to be weeds in the thin spots anyway. Good watering, mowing, and fertilizing will minimize the weeds until fall when you can really do it right.