this might sound looney but...
I always used spit or a little oil from just whiping my finger behind my ear. What I like to do when I first put on a tip the most is use an Iron on a low/med setting and wet the sides of the tip and I bake that FOOL lol. My elkmasters dam near hold up like triangles, which is great so I don't have everyone complaining about mushrooming when I put on a soft tip. BUT BE CAREFUL....I've never messed up doing this but I'm super careful at this and like to wrap the ferrulle with some masking tape to protect it. After the sides are hard in just a few passes, I like to hit it with a fine grit very light and then burnish it with a lil bit o skin oil and a piece of leather, wala beautiful shiny burnished tip that hold up great. Try it on a cheap cue or some old shaft and see for yourself, it really does work very well.
Grey Ghost.