Re: I'm an idiot
Leave your plastics out in the sunlight for a couple of hours before peeling the stickers off. The heat will soften the adhesive a bit, making the job easier. A hair dryer will quicken the process, and your fingernail should suffice for tool needs. Honda Spray/Polish, and/or a little WD40 will get rid of any glue residue.
They make a specific product for applying decals, so you can 'float' them on like the do with window tinting. I know that a lot of people use dish soap/water, but I'd be leary of that method since it doesn't seem like you could ever get all of the soap out. That's just me though. I think you'd be able to find the specialty application stuff at your local auto-parts supply.
Make sure you wrap or box your plastics securely before putting them in the attic, to protect them from rodents that may be tempted to 'taste' them.