No fun doing any of this if you can't share with your friends!
The colors of the primer and undercoat may be slightly different from the factory. And I did admittedly spray more body color on the floor pans than what the factory had. It is hard to stop!!!!!
Anyway, the way I see the underbody on my car is like this: 1) car dipped in a grey/green satin primer. So everything on the car during dipping is this. 2) Then they applied seam sealer by brush to certain areas 3) Beige colored undercoat sprayed to certain areas. None in the trans tunnel and none above the rear axle area. 4) Body spray was applied in the front and rear wheel wells and some along the sides. That is the overspray.
I am not saying mine 100% factory correct, but is good enough for me. I did very little preparation on my underbody as it was mostly intact. So the areas of undercoat applied from the factory, are pretty accurate.