The paint splatter was made in Procreate which is a beautiful iOS application that works elegantly with the Apple Pencil on iPad Pro. The logos were dropped in along with the background and assembled on the template which shows where everything will appear on the truck. More or less.
It’s a pretty simple job, the skin templates are available on ATS modding sites. I got these from IJ’s Mods. The trailer skin is the exact same graphic as the truck skin, but without the logos.
Get back truckin’ on!