One of the best things to do in our area is to aerate in the fall and apply Pelletized Gypsum. Gypsum breaks down clay over time. Also by adding the Gypsum in the fall, it will work into the aerated plug holes and work even better by going through the freeze/thaw cycles of winter and then into spring. If you aerate in the spring and apply gypsum, would recommend topdressing with loam or sandy compost. You really do not want those aerated holes exposed when we get in June, that will only speed up the evaporation of the soil moisture.