Imagine a 1/35 scale figure of a soldier carrying two buckets of water. The arms are separate and after gluing them in place the seam has to be puttied. After the putty dries you have to remove excess putty and trust me, there is no sanding tool in the world that gets into such tight spaces. If anything, you'll damage the areas you don't want to touch.
I'm experimenting (with much success) with brushing the joints with a tootbrush and toothpaste! If done well, this should remove excess putty leaving only that deep inside the joint.
However, does anybody know some kind of abravise paste that's even better than toothpaste? Toothpase is meant to be abrasive on the microscopic level but for the first pass I need something with more bite to it. Tootpaste could be used for polishing/finishing.