There are several processes of cleaning brass gas valve fittings. If you can disconnect your brass ball valve from the pipeline, take it to a sink and run water through at as high pressure as possible. If this does not clear the blockage in the brass valves and fittings, use a small brush (like a toothbrush) and dish soap to loosen and push out the blockage. Spray the lubricant onto the valve where the valve handle enters the actual valve body and let it sit for about 20 minutes. Then, try loosening the valve by hand again. If it doesn't move, or is still difficult to turn, tap it lightly with the hammer.