This document showing how a range of slitless (Star Analyser) spectra were corrected for instrument response using a MILES standard A0v star might also be of interest
http://www.threehillsobservatory.co.uk/astro/SA100_miles_instrument_response.pdf
from this page
http://www.threehillsobservatory.co.uk/astro/spectroscopy_21.htm
The results are pretty good, though some small errors can be seen at the blue end due to atmospheric extinction which was only partially corrected for. Using matched reference stars at the same elevation as each target star rather than a common reference would have improved this.
Robin