"Sticky" zoom on Canon 100-400mm lens

The push-pull zoom mechanism on my Canon 100-400mm lens does not slide as smoothly as I think it should. Obviously I don't want to use WD-40 or 3-in-1 oil to deal with this problem, and was wondering what others may have done successfully. I can't believe that I'm the only one who has ever encountered this. Would it be safe to apply some type of silicone lubricant to a soft cloth and rub this onto the lens barrel? I certainly don't want to do anything to mess up the glass. Thanks for any advice.
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CN