There are various way to clean your brushes, but actually the secret to getting paint out of the ferrule is in drying them:
After you have cleaned your brushes, lay out a paper kitchen towel on a flat surface next to a wall. Place the brush on the towel bristles down and standing upright - lean the handle straight up against the wall and leave to dry.
Any remaining paint will drip down onto the paper towel. You will be amazed that the brushes will keep a perfect shape using this method.
You can do this with all of your brushes except with things like rigger brushes (very thin and long, lay these flat)
I actually clean my brushes with linseed studio soap - any brand will do.
It’s kind of expensive but works like nothing else in my opinion and you don’t need a lot of it.
Shake up the soap container a bit.
I dip my finger into the studio soap and then rub it into the bristles with my fingertips then rinse under hottish water.
I do the handles at the same time. This give the added benefit that it also gets the paint off your hands at the same time (I don’t wear gloves).
Repeat if necessary. Give the brush a really, really good rinse to get rid of any remaining soap.
Brushes will clean up like brand new!
If at some point I forget to clean my brushes and have left them for a few days, I soak bristles overnight in Murphy’s oil soap. Murphy’s is a lot cheaper than studio soap but I find leaves the brush handles kind of ‘sticky’.