use the property address (last known address) if they don't give you a new address when you're ready to proceed. Does your lease state a time they can retrieve items? If not, put a definite number in your next lease.
As for grease in a parking lot,I don't know what it's called but garages use something to sop of oil spills - it looks like saw dust - I believe it absorbs and then you scoop it up.
If you have a substantial judgment already against them, is it worth it to spend the time and money for a few hundred more? Personally, if I were certain I'd be able to enforce a judgment, I'd proceed. If I weren't certain and I already had a judgment, I'd let it go and eat the loss.