Theoretically, you dont need any CAD. The robot doesnt care about actual surface geometry. In fact, you can just move robot axis by axis (or by xyz) "by hand" (looks like this [0]), and teach points as you go.
Usually CAD is provided ahead and you can "teach" the points virtually on PC, simulate it and everything, before testing it with real robot and carbody.
For exterior painting offline preparation is often enough. For interior painting this can be fine, but sometimes you need to move few points by hand in booth coz the CAD usually dont show absolutely everything (think springs holding cardoors closed).
For applying the sealant, where required application precision is in similar range to manufacturing tolerances, it make sense to only prepare program structure, as you need to manually teach every point precisely on the same body that was just measured.
