I would dethatch, roll, aerate then fertilize, in that order. Dethatching will pull the thatch up to expose the soil. Rolling it would correct any frost heave without pressing the thatch into the soil (thus making it harder to get up later), aerating would correct the compaction issues caused by the roller and give the fertilizer and grass seed the contact with the soil to promote seed germination and absorption into the soil. (I am not a professional, just a guy stating the logic I used to do my lawn)I don't have clay soil. It's good black soil. Just wanting to know if plugging will make a big enough difference in getting thicker lawn vs. just spreadin fertilizer alone. I planned on rolling, then plug then spread fertilizer. Would it be best to skip the rolling this year on acoount of compacting ground to much? Would probably cause the cores to not break down as fast. Also thought about pulling dethatcher around after plugs have dried out some. Decisions decisions.
I have been taking advantage of the warm weather and so far have de-thatched, mowed, bagged, aerated, and fertilized with a pre-emergent. I am now waiting for spring show up and do its thing. But my yard was in need some help as I just bought the house in December and it was neglected for the better part of a year. It was 8" tall before I mowed it in January. lol.