One big lesson I learned from the B&O M53 kit was how to safely remove the large piece in the door way. I used a Dremel motor tool with a cut-off disc to very carefully slice through each of the large sprues. The important thing to remember is to brace your hand so that the tool doesn't move and slip on you while you're cutting, just in case the disc binds on the part. I had the body on a piece of foam, which is glued to a piece of wood, and that, in turn, was braced in place. So the body's upper door rail was protected by the foam, and the whole set-up wouldn't move while I did the cutting. This time it went smoothly and without incident. Important Note: I found later in the instructions that if you intend to glue the door closed, then leave the door filler in place, so that the door can be glued to the center rectangular protrusion (I had missed that the first time I read through the instructions). Obviously, if you are going to model the car with the door open, then you are going to need to remove the part.
It was then just a matter of using a sprue cutter, X-acto knife, and mid- and fine-toothed files to clean up the interior of the door way. The next photo also shows orange lines pointing to other manufacturing left-overs that need to be cut and/or filed away. There is a large blob on the underside of the roof, which I cut away just in case it would be visible should I model the car with the doors open. On either end of the under-the-door sills is a triangular piece that needs to be filed away. At each outside corner of the bottom was a small round blob that needs to be cut and filed away (only two of which are visible in the photo).
On my particular casting there was a large gouge on one side of the body. I used a fine piece of sandpaper and carefully filed it away without damaging the rivet details in the area. I highlighted it in the photo, mostly for my own edification for later on (so that I remember where it was and may need to revisit it).