I use products called Rapid Prep and Rapid Tac.
Rapid Prep removes the oils and grime on the surface. Its works so will that I bought a large size and use it to clean the plastics regularly. Preparation of the surface is the most important part to get the graphics to adhere.
After the plastics are clean, spray the surface with Rapid Tac. This will allow you to slide the graphic over the surface to line it up correctly. After that use a small, soft squeegee and work from the center out to remove the application fluid and air bubbles.
Once down, you can use a hair dryer to set the adhesive. Also at this stage you can use heat to mold the graphic around any corners where it doesn’t sit well (most graphics will have a split in the vinyl to accomplish this over complex shapes). Don’t use too much heat as you’ll stretch the graphic and then it will never lay flat over the surface. Always work towards the split.
