I don't plan to rag on regarding jewelry making techniques on this blog because there are already so many other sources of relevant online information. But after manually smoothing earwires for quite some time, I finally invested in Cup Burrs. In my neck of the woods there's a jeweller supply outlet called Lacy's where prices are high and the level of customer service is low. But my husband went there anyhow (100 km out of his way) solely for the purpose of buying cup burrs for me.
Unfortunately Lacy's indicates cup burr size by outside diameter as opposed to inside. They also stubbornly refuse to address the fact that most of the wire available is measured in gauge, not millimeters. So in their usual arrogant wisdom, Lacy's sold David cup burrs that are way too small to be of any use with 20, 22 or even 24 gauge wires! Fortunately he went on eBay and ordered dozens of cup burrs from the states. Well, I'm smitten! These fabulous little tools are a MUST HAVE for every artisan jewellery designer...
The main problem I found in using a cup burr (with any of my Dremels or the flex shaft) was how hot the earwire got, and how quickly it heated up due to the friction. I only hold my earrings in my bare fingers while working, so was getting burned...
But David suggested I try using a cutting fluid. I was skeptical, but wow! now I'm a total convert. In my old bicycle shop (well Jack's stuff really) I found a bottle of Park Tool Cutting Fluid CF-1. It's got a non aerosol pump top so I can pump a little bit onto a cotton ball and dab each rough wire end into that before smoothing with the cup burr.
Being self taught with no background in formal jeweller techniques, I have no idea what type of cutting fluid the 'experts' use. But I can attest to the fact that Park Tool Cutting Fluid (available at bike shops) is wonderful. I think it sells for about $10 a bottle, maybe less, and this product is environmentally safe, biodegradeable, contains no solvents, no mineral oils, it protects and extends the life of your cup burrs and get this as the friction starts to build you can actually see the cutting fluid start to evaporate or even smoke off --- but the wire doesn't get hot!!!
Oh yeah, I've got acute chemical sensitivity syndrome and this wonderful stuff doesn't bother my skin either.
I should state that apparently cutting fluid is available everywhere in many forms and brands so check local hardware stores, automotive supply places etc.