Use a 3D painting software, like mudbox, substance painter or quixel mixer.I would like the car to get stained when going on land, I wanted to create a dust texture. I've seen a video but it's something old from Photoshop.
I wanted the car to have dirt on the body, I have seen cars that have dirt and when the car crashes friction is generated, they told me that this is done by painting the body the AO of the car, and in kseditor you add textures and parameters, but I didn't find any information, only the original of the game, but I couldn't understand how it was painted.If you want the car to have dirt when goes out of track, you need to apply the correct shader to the car and then create a texture map for the dirt. I you are talking about just the texture map itself, you want to either use an image painting software like Photoshop or any 3D painting like Johnr777 mentioned earlier. Explain what you are aiming for and we can assist further.
Pipeline document in the SDK folder explains this in detail.I wanted the car to have dirt on the body, I have seen cars that have dirt and when the car crashes friction is generated, they told me that this is done by painting the body the AO of the car, and in kseditor you add textures and parameters, but I didn't find any information, only the original of the game, but I couldn't understand how it was painted.