I have tried to follow this tutorial to add a livery to an addon car (https://www.gta5-mods.com/vehicles/range-rover-svautobiography-2017). But as someone who is new to modding GTAV, i have no clue what this means:

"Now use for paint materiel > vehicle_paint3 shader
in option :
for detail1 > vehicle generic small specmap
for detail2 > xxx_sign_1.png
mask : vehicle generic mud
and specmap : vehicle generic small spec map"

The addon vehicle doen't have a vehicle_paint3 shader so I went into the xml for the _hi and added a new item for the shader with DiffuseSampler vehicle_generic_smallspecmap and DiffuseSampler2 xxx_sign_1. I don't know if thats what they meant by that instructions.

"and for material option :

alt text

for Detail2 material we chose that photo we created in first step as detail2
now the material is set only start mapping car parts, and doors by each side like 2 left doors and 2 right doors (also yo can cut the bodyshell sides left side with left doors and right with rights doors after finnish attache it back) other parts one by one each that use paint with polygons view but make sure during mapping always use Uv chanel 2 so the car parts gonna be mapped in foxtrodelta_sign_1.png"

For this next part, I followed https://forums.gta5-mods.com/topic/7670/tutorial-zmodeler3-how-to-make-uv-template-livery-template-too to get the UV layout of the vehicle and used photoshop to make a livery texture then imported that texture as rrab_sign_1 in the ytd. Then added the flag into the vehicle meta but still no available liveries ingame.

Am I doing something wrong?