Scold me if you must, but I'm one of those lazy paint brush cleaner uppers and I don't take good care of my paint brushes.
On a good day I tend to just drop them in a tin can of water that contains other paint from other brushes.
And then I leave them.
Naughty paint brush owner.
If I ... think I might plan on possibly maybe some day eventually ... using the same brush with the same paint, I will stick it in a fold top sandwich bag.
For eternity.