Now this is probably not a new technique for you, but for me it is. I have used this technique with other things like lace and flocking, but never my metal stencils. I can't take credit for the idea. It came for Sparkle N Sprinkle.
You will need sticker paper, a static bag, metal stencil and glitter.
Rub the static bag over the back of the stencil (side you will be putting down on the sticker paper). This will let the paper release it easily after you have finished your glittering. Using small crafting spoons start putting your glitter on. I worked from the outside in. Once you have glittered your image removed the stencil and then add glitter to the rest of the image. I then sprayed mine with a clear coat. Not sure that you would need to do that. Loved all the glitz.
Just look at all the glitz!