I suggest taking the slow approach
and finding a better supplier - 287 culls is an awful lot of not much in expectations
I learned on other peoples mistakes - partially cleaned or over cleaned coins that are cheaper than re dirtied bunkos
some other tips:
dont use anything acidic unless its
good silver and even then use it sparingly
clean the containers you use to soak them in every once in a while - I use vinegar and follow that up by a thorough rinsing
cut down the bristles on a toothbrush to half the normal length
1st step for me is almost always a soak in
dish soap and warm water
sometimes a
good boil will break down encrustations - I use baking soda and water in an old
pot - and I do it outside far from the kitchen
you dont need to change the distilled water as often as people think - I change it every 4-6 weeks - or - when it gets cloudy
let the coins dry out before you start scrubbing
I avoid
electrolysis - ruins them in my opinion - other people have different opinion - but I say don't be in a rush, you'll get far better results by being patient
