Ultra-Pure Light Tuning Slide Lube is a safe, all-synthetic light grease that is used on the 1st and 3rd slides of better instruments so they move easier for quick adjustments to pitch.  Just a tiny amount will do.
 
USAGE INFO
Remove each slide and wipe off old grease with a paper towel. Apply a very small amount of fresh lube and push the slide back in.  Wipe off any excess. Do this each week for best results.