1. change your car with JAGUARXKR, SKYLINER32, CAR1004(there is also a bodykit app by aeroaqua
use this tut:
not mine, but helped to understand it.
2. go into the shop buy a IGC bodykit
3. use freeze trainer by Darkteam
4. freeze the parts you wanna keep from your original bodykit(previous car you had)
5. paint car - you will maybe get an error - ignore it
6. change car back to the car you had in UpperCase Letters.
7. viola and enjoy!