- Wash, degrease and polish the plastics before the kit installation;
- Do not use water to install the graphics despite of easier installation;
- Use the heatgun to heat stickers' edges and its body to 70C or 150F and smooth it away one more time after installation
- Leave installed graphics for 24 hours to let the glue to grasp to the plastics.
See the next video, they would be helpful (watch the second with subtitles because it's in russian but nevertheless it's really descriptive).