Used to spray LPS 3 (the thick stuff) inside frame tubes and swab the seat & head tubes. Used the plastic straw through the vent holes and turned the frame to insure coverage. Drained out messy and took a day to dry. To remove external surface rust try Evapo Rust, available at Advance Auto Parts and probably others. The stuff is non toxic, biodegradable, won't harm paint or plastics and works great! For small spots just saturate a piece of blue paper shop towel and wrap it onto the frame tube with clear plastic wrap. Stuff needs to stay wet to work. Instructions say to submerge the rusty part, which works well if it is a small enough part.