A friend gave me a gallon of MF bounce that had been sitting a few years. It was hard-packed probably 1/2" deep on the bottom. I poured off about half of the liquid, then cut the off the top of the jug where it starts to neck down. This let me get to the hard pack with a scraper and a drill mounted paint mixer. It took a while but I was eventually able to get all the hard-pack dissolved into the remaining liquid and then combined it in a new jug with what I had poured off in the beginning.
Sounds like a lot of work bu not too bad. As an aside, I really like that plastic. I poured