Back in the day I shot Kodachrome 64 or 25 exclusively and always on manual. For sun-out days I had memorized all possible Sunny 16 exposure rules. My base for Kodachrome 64 was 500th at f5.6. 250th sidelight. 125th backlight.

For overcast/cloudy days I used an incident light meter.

Unless the light is constantly changing, you can set a proper exposure and leave it there. AEL can be used to lock exposure on something like an area of green grass that is in the same light as a potential subject.

Today's digital photographers like to say they are shooting in manual but they really are not if they allow the camera to select the ISO. With film or Kodachrome, the ISO was always fixed.

These days, I let the camera do the work. I will shoot in aperature preferred, 5.6 or 8 generally and allow the camera to select the shutter speed and ISO. That's for stationary subjects.

For flying bords I set aperature at f8, shutter speed at around 1/2000th and let the ISO go to whatever it wants. Depending on the sky lighting, blue or overcast, I will use the exposure compendsation dial to reduce exposure for a bird against a bright sky. This is for full frame.

Currently I am shooting a Sony A7C full frame with the lightweight 28-60 lens and I also have the Sigma 100-400 for telephoto bird work.  I also have a Samyang 35mm 2.8 and a Samyang 18mm 2.8. Very light kit, other than the telephoto,  and why I switched to the A7C.

I can also adapt my Canon 50mm macro and several other old Canon lenses via a Sigma MC-11 EOS to Sony adapter.