I've been using a Sekonic 308 as my main meter for years, with all kinds of cameras including my M3's (which are my primary 35mm film bodies). I use the 308 in ambient incident mode all the time. I take highlight and shadow readings in every situation, and adjust on the fly depending upon the values in the scene in front of my lens. In bright sun I meter with the dome aimed directly at the sun for highest highlight values, turned away (no direct light on the dome) for shadow values, and then I choose my settings based on the scene and how I want to shoot it. I take meter readings in open shade, bright sun, and darkest shadow areas, almost always with the meter held upright and the dome positioned like a face; this position is the most common way to get a correct reading in pretty much any light. As I'm walking around I just keep metering, putting the dome in highlights, shadows, and mid-tone ranges as the light and scenes change. My meter is always in a pocket easy to grab when I want to check, and I'm always making adjustments to my camera settings depending on the scene and how I want the images to look.
When I was in photography school, we all carried incident meters with us all the time and practiced taking readings in all kinds of light and settings; after a while you get to be able to "smell the light", as an old photographer friend liked to joke. As with anything, experience begets competence and confidence, but especially shooting negative film, this way of working becomes fast, easy, and reliable very quickly. Chrome (slide) film requires a bit more care and precision, but if you tend to shoot one speed of film as your primary go-to, (as I think a lot of us do) the settings you need at that speed become second nature pretty quickly, so that pretty soon you might just use the meter just to confirm your exposures after you shoot as I often do. From there it even becomes easy to adjust up or down a few stops when you load faster or slower films or want to push or pull your main stock.