When I switched to film, there was pretty much only one thing I was worried about: metering. I didn't mind manual focusing (I actually love it and only use manual lenses on my digital cameras as well, except the one I use for video), having only 12 shots per roll, not being able to view my shots, or any other "annoyances" that come with shooting film.

It was all about metering the scene. I didn't want the camera to get in my way of taking pictures and become more a problem than something that should facilitate a creative process.

Smartphone apps

And at first, it was a problem. I was using smartphone apps, which were fine and accurate enough, but cumbersome to use. And there was that notification when picking the phone that would distract you from the composition you were working on.

Light meters

So I decided to go ahead and purchased a standalone, old Minolta light meter. And the thing lasted 2 days in my bag.

You see, I just couldn't afford more things in my bag. A heavy camera with 4 lenses, tripod, filters, film, my digital camera (for video) and what not was already enough.

Finally saw what I'd had in front of me all this time

It took me a while, I must admit. But I finally realized I'd been carrying the perfect light meter all this time: my mirrorless digital camera! I gave it a shot and it's all I use since then.

I set the camera to P mode so it chooses whatever it thinks it's best. You can always change the aperture if it doesn't work for a specific scene. Then I set the ISO to whatever speed I'm shooting my film at. And that's it, you are good to go!

6 reasons why a mirrorless camera is your perfect light meter

It can give you the settings as well as a smartphone app can. Point the camera, and carry the settings onto your film camera.
It can also preview the exposure! Do you want to overexpose or underexpose your photo to create some effect or to darken / lighten a part of your composition? Use your exposure compensation dial (or whatever your camera offers to change the exposure).
It can preview black and white (and probably some special films)! I can set my camera to shoot in black and white, so the preview on both the screen and the viewfinder will be in black and white. After a while shooting only in monochrome I've gotten a bit better at knowing what the result will be like, but every once in a while it's nice to have this little help. Some film photographers used (and still use!) Polaroid cameras for this.
It can preview filters! If you use color filters for black and white photography, and you are not sure about what the orange filter will do to your photo... then just place it in front of your lens and see the result instantly on your screen! Pretty handy.
It works as a log for your photos! Since you are already pointing the digital camera to whatever you are going to photograph, why don't you take the shot? Not only will it work as a digital backup, but it will also tell you the time the photo was taken at, and the settings. Just in case you want to add that information to your negatives as well.

Just one thing to bear in mind

Digital cameras have a hard time with highlights. Film is the opposite: it struggles with the shadows. You can take a RAW file and recover crazy amounts of detail from the shadows. That's why digital cameras will try to be safe and expose more for the highlights.

To avoid losing details on the shadows due to this, I sometimes overexpose my photos, from 1/3 of a stop to a full stop (no more though).

Try it first

I did some testing on this before using my digital camera as a full-time light meter. I took three shots, one with the actual settings, one overexposed by 1 stop and another one underexposed by 1 stop. I compared the results and concluded the camera was pretty much spot on.