For step #2 above, use a film frame that has an area that would print
as pure black for negative, or pure white for slides.
Regardless of the lighting conditions, shutter speed and aperture
of each frame, you should use these fixed values for exposure and
film base color for scanning all frames on the roll of film. Once
you have the exposure and film base color fixed, you can scan the
whole roll of film using these values.
If you're using the same lighting for all the frames on the roll (or
a subset of the frames), you can lock the color balance by scanning
the brightest frame in the series and then setting the Input | Lock image color
option. This will lock the black and white points
for the scene, and will produce consistent colors for all the frames
in the series. This is also useful if you're scanning panoramic scenes
that have all been taken with the same lighting, shutter speed, and
aperture, or if you're scanning a series of studio shots taken with
the same lighting, shutter speed, and aperture.
To optimize workflow, scan to raw files and experiment later with
color correction. Make sure you first set Input | Lock exposure
before scanning a roll of film.