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.

Removing the Built-Up Paint. A paintbrush's worst enemy is paint build up. This is particularly bad. For the best brush, you should find one like the Wooster Brush Q3108-2 with soft brush tips. While a hard brush head is good for increasing the potential lifespan of the brush, the extra stiffness can lead to small imperfections in the finish. Soft brush tips offer more flexibility which creates a smooth and even finish without a lot of extra. Wooster Pro nylon/polyester paint brushes are made with Wooster Pro nylon/polyester paint brushes are made with the very best materials. This unique filament blend was formulated to deliver smooth flow and carry more paint to the end of the brush for fine finishes while achieving it fast.

Not being snarky - being concerned for your health. And your pocket book. I get that.

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.

Fix Hard Paint Brush

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.

Hard Brush Cleaner

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.