When I first began painting, I was pretty careless with my brushes. For the most part I used bristle filberts which held up reasonably well to my vigorous painting style, but not to my neglect. I rarely cleaned my brushes thoroughly: if I did any cleaning at all it was a quick dunking in the OMS and a wipe off. Over time I collected jar after jar of stiff, unresponsive and virtually useless brushes. Most of them should have been thrown away long ago.
Some time ago, I was told about Murphy Oil Soap as a brush cleaner, and I've even tried it a few times with success, but I never paid a lot of attention, frankly. Recently I noticed the jars full of useless brushes littering my studio, and Murphy Soap came back to mind. It's available at any grocery or hardware store, so the next time I was shopping I picked up a bottle. I can't remember what I paid, but it's inexpensive. I partially filled a glass jar and tossed in a few of my worst brushes. I checked back a few days later and found a minor miracle had occurred. My brushes were almost like new...the bristles clean, soft and pliable again. I'm now going through the whole collection of ruined brushes a few at a time. I don't know what the heck I'm going to do with all these "new" brushes.
Here's a picture of Murphy Oil Soap for your information. Next to it you'll see my brushes 'soaking'. One thing you'll notice is that the Murphy in the jar has coagulated to the consistancy of vaseline. I imagine that is due to evaporation of some part of the soap. However, I haven't noticed any lessening of the cleaning power as a result. I just dunk the brushes in the gunk! It works. After a few days, I wipe the brush down and then wash with either a conventional brush cleaner or plain ol' dishwashing soap. I have found a couple of brushes that were beyond repair. If the old paint is too built up at the base (or belly) of the brush, just above the farrell, it may not be possible to clean it out to a new condition. It could be that eventually Murphy would even get that problem, but I figure if it won't do it in a couple of days of soaking, it's not worth the effort.
Nowadays, I'm very careful with my brushes and I clean them properly after every session, but it's been fun to see my old neglected brushes ready to go again. I have more than I know what to do with!
By the way, Murphy works fantastically on dried acrylic brushes also. In fact, it seems to clean them more quickly than the oil brushes.
My Art Site: Bruce Hancock Fine Art