Yeah, I use the county extension office on Roswell road.
also, concerning punching holes in hard clay does not make the
tight soil texture or structure of clay drain any faster. yeah the fert falls into the holes but a good rain will float it out before it soaks in.
if you can manage to get a good deep aeration then you should fill the holes with compost, humus, mushroom compost to build the soil structure and increase the CEC. If you get the soil tested this will give you a good starting point on a fert program. The greatest nutrient availability to the turf occurs at a PH range of 6.5 to 7.5.
otherwise you are wasting fert. I dug out my clay and replaced it with organic topsoil. most areas have no topsoil, just the B horizon which is the sub soil. it does not matter what cultivar of grass seed you have, you can have the best cultivar available, but if the soil sucks so will the results. the soil is more important than the seed. Its a good idea to increase the tilth of the soil to a depth of 6 to 8 inchs for excellent results.