About 60% of my exposures are by sheer guesswork based on the "Sunny 16 rule". Most of my cameras don't have built-in meters, and a loose meter is too much of a bother when the camera is small. I will happily use two different meters for LF, but for MF and TF (tiny format, AKA 35mm) I just can't be bothered.
More than 90% of my negatives are printable, even if they may not be worth printing... Every onece in a while I run a slide film through one or the other camera. I gues exposures then, too. It's just a matter of practice.