Hi Andy, I think your approach will work well with well isolated lines where you can be sure all the flux is from the line you are interested in. Where lines are blended fitting a Gaussians (or other line profile) allows you to deblend them, at least approximately. The biggest problem I have is that there is no obvious continuum in the yellow hypergiants which is why I am attracted to the idea in the paper of subtracting the fitted profile from the spectra to give a new estimate of the continuum.
I am going to experiment with SPLAT and see if taking different starting continuum levels converges to the same value in a few iterations – I easily lose focus!
Regards Andrew