Hi,
I did a lot of slide film. In third year slide film was used at my school to make students be sure about exposure, after two years of B&W negative film.
Slide film and E-6 are sooooo easy because a) you see the positive, and b) there's just one possible development.
It's this simple: incident metering for direct sunlight. Your highlights will be perfect. Comment: you can open a third or half a stop if you want more open skin, as for fashion. You can close a third or half a stop if you have no skins and you want the highest color saturation.
For overcast or shadows (soft light) we don't reach clean whites after an incident reading: you"ll need a little more light. Do a 7 frames strip (bracketing) in thirds, from 1 stop overexposure to 1 stop underexposure (under soft light) and the same under direct sunlight, both incident metering, and you'll see perfectly what you need to decide after your own meter reading.
B&W film is totally different. There are two fields: a) adjusting your scene contrast to a single sheet, and b) mixing scenes of wildly different contrast in a roll, so for mixed scenes we need a short development to be able to print sunny scenes without blocked highlights, and we just expand the contrast of soft scenes with higher contrast multigrade filters while printing. Both work. Of course in the mixed scenes case, the shadows of sunny scenes are a bit darker than if we do sun perfectly for a sheet.