I'd dip the paint back in the liquid glue until it's nice & soft (don't let the bristles rest on the bottom though), and then wipe it clean on a piece of kitchen towel. That should return it to 99% of its former glory
You should try a Touch'N'Flow applicator from our friends at Aeroclub. It's a glass tube with a tiny steel tube applicator. it's great for applying small drops of liquid glue, and capillary action does the rest. I don't know where I'd be without mine now. I think they're about a fiver each, and you'll soon get through that much value in brushes, as they tend to lose their "nature" by constant dipping in glue.
If you do get one... don't leave it on the bench, as it'll roll off & smash - ask Nige. I keep mine upright in half of its packing tube, which is velcroed to the side of my spray booth near my tool rack. Stops it going anywhere, and if you store it applicator tube up, it reduces the instances of it clogging with glue debris