I've just made the decision to go organic for my lawn. Here is some background and then my question.
Lawn is in good condition. Live in Northern Utah. Lawn is a standard Kentucky, Rye, combo for cool climates. I've fertilized four times a year using synthetic fertilizers Spring, Late Spring, Summer, and Fall. Lawn is small enough that I pull weeds by hand. No herbicides and no pesticides. For summertime I keep lawnmower deck height at its maximum (3.5 inches). I leave lawn clippings on the lawn and rake them in after each mowing. I use Aerify a couple of times a year to help "soften" the clay we call soil in these parts.

My Question - When should I add a compost top dressing? What type of compost should I use? I don't have a truck (and I'm not willing to rent or borrow one) so municipal compost is out. Is big box stores bagged compost good enough?