Personally, I don't like using royal icing because it just doesn't taste very good. Instead, I dip my cookies in a fondant icing like the one at this link (Quick Pour Fondant Icing - Allrecipes ). But, I usually use milk instead of water and leave out the almond extract. Add coloring if you want.
Just dip the top of your cookies in it and they will have a nice glossy coating. Don't stir too much or you'll get bubbles in your icing.