Hey everybody,
Just wanted to let you know how this went in case it's useful for anyone reading the post later!
First, I followed jimijam's advice and used the photo paper-best quality setting on my printer. It looked fantastic!
Next, I followed the advice of a couple of you and picked up some Testor's Decal Bond spray (last can at the local hobby store!). This stuff works great! I only needed to let it dry about six hours before I could get it into the water with no colors running. I did the three coats as TNblueshawk suggested, and also cut it out before spraying. In the future, I think I would probably affix it to a slightly heavy piece of carboard with a small piece of double-sided Scotch tape before spraying. Since I had cut it out already, the force of the spray almost made the decal get airborne and flip over!
I didn't have any problem soaking it and getting it onto the enclosure, but it was then I realized I cut it a bit smaller than the face of the pedal. Totally my fault--I used the 125b enclosure border from the pedal vector pack to create a nice border for the image. I decided after holding it up to the enclosure that I liked it better without the border, so before I sprayed with the decal bond, I trimmed it off. I probably should have redone the image a bit by scaling the border slightly larger than the enclosure face and then just using it for a cut-out guide.
I think I managed to squeegee the water out pretty well, minus one issue. The drill holes on the enclosure face seem to have very slight lip on their edge, and it was very hard to get the water and bubbles to exit via the hole or to move them out via the enclosure edge. As the decal dried, I could see these slightly cloudy areas around the edges of the holes, and in a couple of other places. Still looked good in the right light, though!
Trimming the holes out went fine. Then I clearcoated with Rustoleum automotive gloss. All was well until a gust of wind came after coat number two and made the newspaper on which I had set the enclosure jump up and slap the clearcoated sides! I quickly pulled it off, smoothed out the goofed-up areas, and re-sprayed. Next time, I will anchor the edges of whatever I am spraying on! All in all, I did quite a bit better than the first time I clearcoated a box. Under light, you can see some slight ripples on the face of the enclosure. Does that mean I should have held the spray can slightly farther away?
Anyway, this was a fun and educational first attempt with the decals. I don't think it will look too bad once I dress the box up with the knobs, switches and LED. We'll see anyway! Unfortunately it will be getting cold here soon so I might be done until next spring. Luckily most PPP enclosures look good without decals.
Thanks again everyone!