I need a lot of painting handles as I usually working on several miniatures at the same time. This is partially because some of miniatures are painted with oil paints which dry slowly. Tried some of the handles, but finally I am using two type of handles. One is the orange medicine bottle and another is wine cork as in below photo.

To attach the miniature in these handles, you'll probably need blue tak or plasti-tak.

To prepare the medicine bottle, I added some pebbles to give extra weight. Then, I glued regular white paper using Mod Podge, then gave a coat with acrylic Gesso. The reason I put the paper/gesso is to give a nice texture so that the plastic does not feel slippery. This is especially true if you have oily skin.

To use the cork, try to find champagne cork instead of regular one as champagne corks are larger than regular one. I bought 25 used corks only costs $3.25. For used corks, try to boil the cork in water at least 5 minutes. This will sterilize them, and it helps to expand the cork in the original shape. I like the feel of the cork texture more than plastic, but they are light-weighted, so try not to flip your still-wet miniatures.

You could attach a stability handle to the cork for better grib. I used large paper clip bent, and attached to the top of the cork. Photos explains better than words: