Use a pastry brush to brush the beaten egg on the item you want to add sparkle to. Then sprinkle it all over with sugar and set aside to dry. If there is a stem, grab onto it while you sprinkle. If there is no stem you can plop it right in the sugar. For single berries just drop them in the egg white and then roll them around in the sugar with a spoon. For things like pine cones and sprigs, you can just brush their tips.
You can dab more egg white on spots you missed, and re sprinkle with more sugar, but try not to be a perfectionist about it, you're going for a naturally frost kissed look.
For this demo I used what I had lying around the house (and yard!) to make an impromptu centerpiece...the mini pumpkins leftover from my Halloween decor, a few clementines, pears and concord grapes. I added some pine cones and a few pine sprays for fall flavor.