wash,
clay, polish, glaze then NXT.
Between the claying and polish, whatever was on the paintwork will be gone. The cleaners in NXT are likely to cause problems "layering" but it is advised to apply two "layers" to ensure complete coverage.
As for a polish or glaze? If it is relatively new and swirl free, then something like vanilla moose or Megs #80 should do the trick. Slight swirl removal and glaze all in one, then follow up with your NXT.