what to do first, put fertilizer step4 or reseeding new grass now ?i live in chicago?

Step 4 in 4-step programs can be replaced by a seed started fertilizer for a year. In fact, some fall fertilizers say right on the bag that they are excellent for seed starting.

So get the areas ready that you are going to reseed--get out enough of the dead stuff that the new seed can touch the soil. Put your seed starter fert. or fall fert that says its good for seed starting in mid to late Sept. then put down your seed. If you are in a windy area which you probably are if you're in Chicago you may want to put some straw to protect the seed from blowing and washing in a heavy rain.

if your gonna fertilize do it now, then wait about a week to a week and half to overseed. in the great lks area this is the beginning of the best time to estabolish a lawn. 1-pleasant temps not hot enough to bake the seed, 2- begiining of rain season, lots of natural moisture. 3 the ground remains warm enought for grass seed to pop even after halloween. then next spring as soon as the snowmelts re fertilize with like a 28-3-3 mix w/ weed killer enjoy your green lawn

Weed and feed spring and fall. Overseed in the spring. We're north of you and that's how we do it.