I haven’t found a non-messy way to do this. First, I would suggest using the Resin Obsession crystal doming resin. You can buy it in our store here: https://shop.resinobsession.com/collections/resin/resin-obsession-crystal-doming-resin It will give the thickest coating.
Next, put the bead vertically onto something thin (toothpick, pin, etc.) that is either wax coated or sprayed with a good mold release. Vaseline may even work. Using the toothpick example, put the bead onto the toothpick. (Hopefully, the bead stops on it at some point.) Push the toothpick into a base (styrofoam works well). Brush on the resin and allow it to drip off the bead. Once cured, take it off the toothpick. You may have to sand a little resin, but hopefully, it won’t be much.