She said:
“also I read the suggestion about covering the needle with nail polish and sanding the tip so you don’t burn the surrounding skin. has anyone tried this? is it a good idea?”
I think no one answered that part of her message and I am curious about the very same thing 
.
Anyone knows the answer?
By the way, what does “sand” mean in this context?
Does it mean that you have to put nail polish all along the probe BUT in the tip? or something else?
The nail polish trick is a way to try to turn a non-insulated probe into an insulated one. How far down to put the nail polish depends on the depth of the hairs you are treating. Studies suggest that you need to apply energy to two parts of the hair for most effective results: the root and a bulge area about two-thirds up from there. In other words, you only want the nail polish to go about a third of the way down from the skin surface to the root. Since each hair has a slightly different depth, this can be tricky. As a rule of thumb, I’d suggest having the polish go only about a millimeter into the skin (about a dime’s thickness) when the probe is fully inserted. That way it would lower the energy to skin right at the surface, but it would apply full energy to the bulge and root.
once you have covered the entire probe/needle with polish, you will need to remove some. This can be done with Sand Paper, Of course, you could try to leave the bottom of the tip out of the nail polish when you cover the tip so that you don’t have to sand it, or try to use nail polish remover on just the bottom.
Professional probes are polished and any scratching makes insertions more painful as the polished surface is destroyed, and the sliding of the probe becomes the scratching of the scarred surface of the metal you leave behind.
Just one more reason to go to a pro instead. If you insist on doing it yourself, try to get a friend to help you do it to each other.