snip
With 12000 square feet, good seed really isn't going to be cheap and
you have the rental cost of a slice seeder to properly sow it, plus
all the labor. This is one of those things you can do right once, or
keep doing wrong many times.

Totally agree. I'd love to scrape it up and put down a nice new
suburban lawn- amended soil, roto-tilled..... time and money prohibit.

What I've been doing is occasionally throwing some seed and dirt,
sometimes that foamy Scott's lawn patch stuff, into the little gaps in
the lawn. Grass fills in during the spring and it does look really
lush, but the issue is still the 4 different types of grasses.
Squirrels rip the shit out of the grass right about now, bury acorns,
looking for grubs, bulbs, whatever, so seeding now is kinda tricky.

The fellas at the local True Value could probably steer me to the
right seed type (fescue?), but I'll have to use that same exact type
of seed for the next few years. I think I'm kinda stuck doing it this
way unless I replace up the lawn a section at a time.