Here's what works best for me, and I get very good results, IMO. Printers and other factors will vary, so this may not work the same for everyone.
I use inket WHITE waterslide paper most of the time. Clear waterslide paper is great for pedals with a lighter finish, but darker finishes will call for a different course. White paper gives you much more options if you are not trying to see the base coat through the decal. This is the best options for printing a decal for a dark colored pedal. It also gives you the option to have white text if you have a solid colored background as part of the graphic on the decal. I often just match the color of the pedal in the background of my image, so when I put it on the decal, it blends with the base coat. Obviously this doesn't work with all finishes, like sparkle. A helpful hint I would give anyone using white waterslide paper is to color an edge or a border on your graphics as close to the color of the pedal as you can. If it is bare aluminum, just use a light grey. This will help if you don't cut a perfect edge on your decal because it will blend into the pedal better.
I vastly prefer the Papillio brand of waterslide decal paper. It works great with my inkjet. It takes the ink well and doesn't crackle or fade like some other papers I have tried. The Papillio white is almost opaque, even on a black pedal, so there is no fading. It also resists tearing and stretching. If you're using the Testors stuff, I never liked the way they came out, in clear or white. Your printer may have different results for you.
After I print my decal, I let it dry overnight. No rushing to clear coat, just wait overnight. The next day, I use Duplicolor Acrylic Clear coat, the kind at Pep Boys or an auto parts store. I tried a few different brands, and that one works for me. I put 4 light coats on, 10 minutes apart, then wait overnight for it to dry.
Next, I clean my enclosure surface with alcohol. Then I put very slightly soapy water on the surface while my decal soaks, completely submerged in warm water for about 10 to 15 seconds. I take it out and let it set on a paper towel a few more seconds. Then before attempting so slide it, I gently bend it back and then forth just to help break the decal free from the backing. I slide the edge slightly off the backing and place the decal in place, flat on the pedal. While holding it in place with one hand, I slide the backing out from under the decal. Then I use damp paper towels to center it in place and smooth it out. Once it in place don't mess with it, and wait overnight until your next step.
