How to make door seams on car model

Ive model a vehicle body and want to know how to create door seams and split lines in the body ?

Car models are 95% realized with several objects like the real car. So instead of making seams for the door, cut in a hole and make an actual door. Only a few game models are made of one object, but due to complex physics and damage models, state of the art/tech game cars consist of dozends of parts.

If you insist on making “seams” on the car model the quickes way IMO would be to subdivision model the doorseam as one loop, bevel it, extrude it and shrink/expand it, then set an according crease to the sunsurf modifier, maybe add an edgeloop in the extruded, shrinked loop… just play around till it looks good.