I know, Myself, am not trying to be a condescending ass about it. Its a honest serious question/suggestion to use one. .
Ive mentioned this before, my father in law was VP of Chemlawn and in sales and went to OSU for agronomy. To this day, he still uses a walk behind spreader at our house and a tow-behind at my sister in laws who has 5 acres.
Penningtons is good brand and you can walk into any store and they will tell you what you should be fertilizing with in the current time of the season.
right now, its feeding- next month its pre-treating for weeds
While i am not a fan of scotts- (their stuff is full of filler crap according to my FiL) Here is a decent "schedule" of what to do.
its not difficult.
If you need work done to fix certain areas, those are different questions that plenty of us can come forward and help with. (clover/oxalis, dead zones, when to seed.. yadda yadda) How short/long to grow your grass.