You can probably use a small wire brush to get the rust out of the frame and for the future use JP Weigle Frame Saver spray. It acts as a rust inhibitor so should slow down/stop any rust forming on the inside of the frame. You can get frame saver at JensenUSA (I'm sure there are lots of other spots too).

http://www.jensonusa.com/store/product/CM407B04-Jp+Weigle+Frame+Saver+Aerosol+Can.aspx

You can probably use a small wire brush to get the rust out of the frame and for the future use JP Weigle Frame Saver spray. It acts as a rust inhibitor so should slow down/stop any rust forming on the inside of the frame. You can get frame saver at JensenUSA (I'm sure there are lots of other spots too).