Personally, I have found that the meters on many DSLRS are accurate, in that they produce repeatable results, but are often not calbrated to the represented ISOs. Your answer is to use the same meter (whether it's the camera or a hand-held) all the time and a LOT. Through trial-and-error, you will develop a feel for how it's readings correlate to your film speed. Then you're laughing.
For what it's worth, my best friend does all of his LF metering with his Nikon F6, and it works just fine, since he's learned its characteristics.