Keyda - might try this trick on putty. Put a layer of masking tape on each side of the seam, leaving about a 1/16th inch from each piece to the seam. That keeps it off of what you don't want to putty, and also gives you the thickness of the tape to sand down to. When you hit the tape, you can pull it and finish sanding. Also helps in preserving panel lines and rivets.
Making progress on it, glad you are feeling better.