This is a messy way to go. You need a thinner bucket. I don't understand why commercial painters love to fling thinner around, it's a toxin and a fire hazard. Anything you aerosolize, you breathe.
Purdy 3-Pack XL Nylon- Polyester Blend Angle Multiple Sizes Paint Brush Set. The Purdy XL brushes feature the iconic copper ferrule. Purdy loads the brush with just the right blend of Dupont solid, round and tapered Tynex and orel filaments for brushes that perform no matter what the job.
Not being snarky - being concerned for your health. And your pocket book. I get that.
- If the paint is hard to remove, try adding a little dish soap and massaging it into the paint brush bristles. If you used oil-based paint or stain, clean the brush by soaking it in mineral spirits or turpentine. Plain old water will not help here!
- Saturate The Brush Bristles With Warm Soapy Water. First things first, let's get those.
- It can be a challenge to remove old, dried paint from brushes, but often the effort is worth it. Effectively washing a “petrified brush” can spare you the cost of buying a new one. Soak the brush with hardened paint in vinegar for an hour. If the bristles don’t bend, soak for an additional hour.
- Cleaning Hardened Paint Brushes.
I was trained to clean those brushes after the day by wiping them out, giving a good rinse in a thinner bucket to knock off any solids, and shampooing with Murphy's. Every Day After Painting. There's no reason for a brush to get to this state. The next morning, it's dry and clean and ready to go. You can also knock off any cruddy build up through the day in a thinner bucket. Which is a zinc or steel bucket, with a lid, with a grate inside to run the bristles over. Paint solids fall to the bottom and the thinner can be used until it's exhausted. No breathing micro droplets, none on the skin, and the fire hazard stays contained. Yes, paint thinner is a fire hazard. It comes from the same cracking tower as motor oil and gasoline, it's very dirty stuff. It often contains lead and other nasty things too. You don't want to breathe it.
You can also give most brushes a 72 hour soak in Murphys as a maintenance deep clean. Every six months or so. This can also rescue brushes you've already trashed. No scraping or grinding needed if you clean up every day though. That's time out of your life. Go watch a game! The five minutes to wash brushes is worth having a clean dry well conditioned tool at hand the next morning. But a Saturday afternoon? Nah.
Cleaning Hardened Oil Paint Brushes
I'm trained as a portrait painter, but I renovate houses too. And I have a brush fetish, I have over a thousand high quality ones. I clean them all the same way, studio or house. They're all in great shape. Washing daily is not a problem, the oil in oil soap is a great conditioner for natural hairs. Just let them air dry out in the open, they could mildew in a closed container. Takes them inside in freezing weather. Love them and they'll love you back.