I'm trying to achieve a specific look on my MP figures, but Reprolabels looks a bit too "sticker-y," and I can't print white onto WaterSlide Decals (and I'd rather not cut white outlines). What do you do, to make your figures' faction symbols look like they've been tampo'd at the factory? (see Prime's shoulders here: https://i.ytimg.com/vi/lJcFFhDWznQ/maxresdefault.jpg )
Testors decal system paper comes in white and transparent. I love the way it looks, and if you follow their system, you can do just about anything with them. For the look of Optimus you referenced, I'd to a decal on white paper and paint the raised part silver/gray. I love reprolabels too, the quality of their stickers, especially on transparent plastic is beyond anything you'd do at home. But if you need something custom, the testors decal system is the way to go. Not too much of an investment and it really can bring your vision to life. My Death Proof Cliffjumper in my signature is a custom waterslide decal.