I tried (and got rid of) the PowerVibe, just didn't work for me. The sifters work, but the reservoir is usually too small and takes a lot of refilling. And if you live where there's a lot of humidity, it can be a pain getting the powder to fall correctly.
I generally use a jeweler's tweezers to lay in powder detail in pate de verre. That's a long pair of tweezers with a flat, square scoop on the end. You can get them from jeweler's supply stores.
You fill the scoop about half-full of powder, tap it gently to settle it, and then draw it along wherever you want the line. There's enough vibration, usually, to slide the powder out in a very thin line. Once you get the hang of it, you can draw very straight lines with it--curved lines take longer to learn.
If I really want precision in pate de verre, though, I do more of a subtractive process, removing the powder I don't want to create the line. I have three square, flat-edged and very soft brushes I use only for this: Dip the very clean brush in water and touch it to a paper towel to drain off the excess.
Then rest the brush at a low angle on the refractory, touching very slightly below where you want your line. Push the brush into the exact edge of the line, and then lift the brush straight up. The damp brush will pull the excess powder cleanly off the refractory. Dip the brush in water to get rid of the powder, and repeat.