Clean,clean,clean. Then clean again. I recently won the Germanfest concour in Brookline Ma.
They judge everything, the car has to be original, no aftermarket anything.
when I say clean I mean everything. They will even pound on the seat to bring up dirt.You should do this also to get the dirt that vacuming won`t get.
I lose points because I have an Optima Battery, but it`s better than corroding the frame.
When I won this show, I beat an SEC from Hatch and Sons, who is a world renouned restorer of Mercedes.