Lots of good tips here, but let's stick to the original posters question about cleaning that area between the top strap and the barrel. As another poster mentioned, it's always a good idea to not let things get too fouled up. That said, if that area of your revolver needs some work to get back to pristine condition, try this:

Go to your local Ace hardware store and get a short length of quarter inch brass tubing. Smack one end flat with a hammer. You now have a scraper to dig out that lead accumulation in that area. The brass will not harm the finish on a blued gun. Sometimes you need to soak a Q-tip in solvent and simply jam it into that barrel/frame juncture and let it soak for a while. You can always renew the edge of your brass tube scaper by cutting it off. Use a good brass cleaning brush to work this area. On stainless steel guns, I will put a dab of Flitz on a patch and simply draw it back and forth through that barrel/ top strap area to get things spotless once that lead has been removed. Resist the urge to use anything steel to scrape this area. One slip and you may have an unsightly scratch.