"broekzwans"
- The answer is yes ! You have to be sure not to score the barrel so DO NOT use a brass cleaning brush from a traditional gun cleaning kit. I use weed whacker cord and cut a length roughly 8 inches longer than the barrel. Next just heat one end up and flatten it out so that the wads can be slipped over one side but wont fall off the end as you drag it through the barrel. Lastly just run it through and use new patches as needed, doesn't need to sparkle but it shouldn't take more than 5-10 runs.
Brass brushes won't hurt your barrel if you use it in a normal way. Just don't pull it backwards while the brush is in the barrel and go easy on the crown end. The barrel steel is harder than brass so it won't harm it under normal use. I think this "myth" comes from the time that some barrels were made from brass because it was cheap and easy to make. Using brass brushes in brass barrels makes it highly likely to get scratches in the barrel.
Nevertheless, you'll probably never need a brass brush in airgun use, the nylon brushes will do the job just fine in almost all cases.
The weed hacker string is a very good tip! I use a similar idea, a nylon rope with a shrink sleeve around it, same idea and functioning.