If your shooting Triple Seven powder, simple spit will work fine for a liquid swab material. No need for a brush really. Put a CLEAN patch (if they are dirty you will taste it) in your mouth and suck on it. When your ready to shoot take that patch from your mouth and swab the barrel with a tight fitting jag. Then a dry patch or two and your set to shoot again.
I personally run out of spit, so I use a 50/50 mix of isopropyl alcohol and car windshield washer fluid. I spritz a patch and swab. Then a dry one or two. I fill up an old OFF bug juice pump spray bottle. Hold that patch and spritz it. It works real good and is easy to carry in my range bag.
I have also used simple cleaners. A good one is Simple Green. That stuff is like 409 and it will take and really clean out the bore. I have used a product called Rusty Duck also. Wal Mart had a end of season sale on it for a $1.00 a jug. And they HAD 12 jugs. So now I have a lot of Rusty Duck. It really cleans fowling good in rifles.
A friend I shoot with, uses the left over water from when his wife does the dishes. He fills a old Dawn soap plastic bottle with it, and has swabbed his barrel for years with that. He claims that's why his wife has to do the dishes so often...
Almost anything will work. The main this is be consistent when you swab. Also that brush can help if your shooting a lot in a day. Lets say you have twenty rounds through the rifle. And you want to shoot more. Run that brush with some solution down the bore and back out a couple times. Turn the rifle upside down, and tap the muzzle on your shoe. It will know some of the stuff out. Then swab as normal.