Once the domain of Thunder Chicken hood stickers and sponsorship decals, vinyl appliques have taken on an entirely new significance in recent years. Vinyl body wraps and custom body-forming accents have made serious inroads into the legitimate custom scene, offering all the visual impact of a custom paint job at a fraction of the cost in terms of material, labour and later repair. There's a bit more to applying vinyl than simply sticking it on, but it's nothing that the average gearhead can't do in his driveway.
Wash the car with a mixture of dish detergent and water to rid it of any surface contaminants and old wax. Dry the area with a lint-free towel, and then clean it with another clean towel and rubbing alcohol. The alcohol will get rid of anything on the surface that the detergent didn't remove.
Set large decals out in the sun for an hour or so. This will soften the decal and allow it to more easily conform to the curves of the car. Park the car itself in a shady area, but don't apply the decal to any surface outside of 10 to 32.2 degrees Celsius. The ideal ambient and surface temperature is between 26.6 and 29.4 degrees C; warm enough to keep the vinyl pliable, but not enough to make the adhesive gooey.
Mix up a solution of four to five drops of dish detergent or Ivory liquid soap to one quart of warm water and pour it into a spray bottle. Spray a liberal amount of soap solution onto the entire decal-application area, and keep it moist during application. The soap will interfere with the adhesive, allowing you to slightly reposition the decal and squeeze the bubbles out.
Pull the opaque backing material off of the decal and have an assistant help you to position it on the car. Do not spray the back of the decal itself with soap solution, or it may slide off the clear transfer film. Position the top of the decal exactly where you want it, then hold the top in place and start smoothing it out with your palms in a downward motion.
Spray the top of the clear transfer film with a liberal amount of soapy water and start going over it with your squeegee to seat the decal and drive the bubbles out from underneath. Work in small areas, making sure that each is perfectly smooth as you go. Once most of the water squeegees out, bubbles might get trapped in the now-dry adhesive and prove impossible to remove.
Pull the clear transfer film off of the vinyl, very slowly and carefully. The adhesion still isn't complete -- that takes a full 24 hours -- so yanking on the transfer film may well disturb or remove the decal.
Wet your hands with soap solution and gently run them over the decal to smooth out any wrinkles and remove any bubbles that you can. If and when you come across a bubble that you can't remove, prick it with a pin and press it flat. This might cause a slight wrinkling in the decal; smooth it out with your wet fingers.
Pat the area dry with a lint-free towel and allow a full 24 hours for the adhesive to set.
If you have trouble getting your decal to conform to a hard curve on your car, you can soften and stretch it a little using a hair drier set on medium heat. But don't stretch it too much; vinyl decals stick with an adhesive, not by static friction. Stretching it excessively will just create a thin point in the vinyl and open the door for cracking and peeling later.