The first house we bought was similiar to that. Had 5 acres with junk everywhere; in the yard, in the house, in the basement, in the barn, the crib, the milkhouse, yuk, yuk, yuk, yuk! (Got a great deal though!)
After they moved "out" we emptied the house! Took a 20 cubic yard dumpster just to empty the house! (not to mention the amount of cleaning it took to realize the kitchen floor was off-white, not the dark gray it appeared to be) Had to remove carpets and treat sub floors with ammonia, bleach, etc. Wife would not use the toilet until we gutted the entire bathroom down to bare studs and floor joists and then rebuilt the entire bathroom. Took 3 weeks to get the house liveable before we moved in.
Then the yard work started! It took time and perseverence (and some seat time on the ole' Ford 9N with a boom pole for large items) but 4 - 20 cubic yard dumpster loads later we could use a mower on the yard! Wow! Don't need to go into all the details but suffice it to say that we found dirty diapers and their youngest was 11, no trash pickup in 8 years! Ughhh and , and and ....!!!
That cleaning process alone increased the property value by $15k. Sure would have been alot faster with a FEL.
Buster57's suggestion of renting a small tractor with FEL and aerator is great (don't forget the insurance)! Sure would make it alot easier and less time consuming.
I don't envy what you are facing but it sure is a great feeling when you get done.