Did this myself & worked great. Unbelievably great..
Moved to a house that the previous non's did nothing in the yard except rake
the pine tags into two piles in the middle of the front and back yards. Used
pine tags elsewhere and obviously there were two deader than dead spots. Dug
up 4 or 5 spots in inconspicuous places in March and replanted my "plugs" in
the bare spots after liming about a month before. (used pulverized lime and
worked it in with a garden rake and kept wet). After applying pre-m without
n-p-k, I then went with 13-13-13 and when cutting grass, I bagged it and
kept a 3" layer of clippings in the bare spots between my plugs and the
spots from where they came from.
By late June you could not see where the pine tags had been and the grass
was all the same color. I got to stay on my fertilizing schedule and
re-seeded in the fall.
I normally use pelletized lime though, twice a year, here in central Va.s
acid belt..