There is actually two different problems happening when we see the ghosting images.
In the case of shaved details, the plastic in the details cools at a different rate than the thicker plastic around it after it comes out of the injection machine. Of course I'm only talking about a few seconds, but it 'tempers' the plastic differently and is harder. When we cut off handles, or chrome trim and sand it flat, there are two different surfaces that must be dealt with. The 'ghosting' in this instance comes from the plastic reacting to the paint differently because of the different hardnesses. When you cut off detail, you can notice that the plastic does not have that hard, crisp shine that the untouched plastic has. That crisp plastic is like a shell and the exposed plastic is the softer insides.
As far as the putty, even seven days may not be long enough for it to completely cure. The outside may be hard enough to sand, but the layers underneath may still be a bit softer. Definitely apply thin layers of putty and let them dry between applications. I try to use the same plastic as used in the kit to make a slurry filler with liquid glue.