I have not had much luck with the penny trick, or with a brown bag trick...
If you get a 12000 grit micromesh, you can use it fairly safely to polish the tipping if your intent is to keep things fairly round. Because micromesh is mounted on foam it will "wrap around" the object you are sanding, even with fairly little pressure, and will round things somewhat.
If your tipping is stubby or italic, I would go with a lapping film of 0.05-0.1 micron grade, mounted on an old credit card (via double-sided tape) or some other such stiff surface. That way you can smooth the tip without rounding it off too much.