There is a specialist silicon lubricant you can buy from brass musical instrument shops that helps with this problem - both prevention and cure. Otherwise, WB40 will help. Force is the last option as there is a good chance that one or more stays will break away and need re-soldering and/or the slide hits something and gets damaged when it suddenly comes free. Believe me, I've been there a thousand times!
Simon Croft
June 2010
Try expanding the brass by immersing it in very hot water, and pulling hard.
John
August 2009
Automatic Answer
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