A ball jag is made of softer steel than your barrel and will not scratch it. Brass is too soft for the job, as it will twist off before it pulls the ball. Put some oil down the barrel and through the touch hole to wet the cloth patching in the barrel. Give it some time to soak in. Then use a standard ball jag on a steel cleaning rod, and run it down, and then put as much pressure as you can while turning the screw into and through the ball. Then get someone to hold onto the gun stock while you pull the ball out.
I have used a pick and a hardened metal scriber to move a lead ball forward by putting it through a touch hole, but this obviously depends on the size of the touch hole, and the bore of the gun. The smaller the hole, the lest movement per insertion and levering you are going to do. If you can move it forward enough to get flash powder behind the ball, you can fire the powder and it will push the ball forward enough that you can put 5 grains of priming powder under the ball, then seat the ball back down on the powder, and fire it in a safe direction. The ball will exit the barrel and travel only a short distance.
You probably will have to move that ball forward some to be able to use that CO2 device to blow it out. If the ball is right back against the touch hole, there may be almost no place for the compressed air to go. Again, with a hardened metal scriber, you can go through the touchhole to move the ball forward mechanically, with lots of patience. I would rather use the ball jag and just pull the damn ball out, as I have had to do this on more than one occasion, and I know how to do it, and what it feels like to get the ball moving. BTW, that jag will misshapen the ball and patch, and in doing so, loosen the contact between the barrel and the PRB that got it "stuck " in the first place. With the oil poured down the barrel, its surprising how easy that ball comes out on the jag. If I had fired the gun before I dry balled it, my barrel was always clean with lots of crud visible in the patch that I pull out. To lap a barrel once, I took one of those balls that had been stuck in my barrel, wound it back down on my ball jag, and then used a piece of patching with JB bore Cleaner on it. to lap the barrel. It took a couple of sharp blows to get the patch and ball started in the barrel, which I had oiled again, but once it got it started it sent down the barrel easily, and I could actually feel the rough spots as I worked the lapping compound over it until it was gone. Most of the time, I just use a couple of thick patches on my cleaning swab, covered in JB Bore Cleaner, and depend on lots of strokes and lots of sweat to get the job done.