Probably the fastest and easiest way to cover the bases would be to do automatic exposure bracketing. But if you want to be precise, I'd say either use an external light meter, or get really really good/fast with the Sunny 16 rule, and learning to use your histogram to judge exposure.
The Sunny 16 rule is a good way to approximate for exposure. In clear, sunny skies, assume you can get a decent exposure with f/16, and 1/iso_setting. So, at iso 100, 1/100s and f/16. Or iso 200, 1/200s and f/16. Then adjust and swap stops in your head from there as your starting point.
And then, when you've taken your initial image, look at the histogram for the image on the LCD. Those vertical lines on the histogram tend to correspond roughly with stops of exposure. So, if you need to move things 2 bars around on the histogram, then guesstimate a 2EV (2 stop) adjustment.
Practice, of course, should help to speed up and reduce the number of test frames.
An external light meter or light metering app might be another way to go. Since an external meter is likely to let you take both incident and reflected light readings, it could be more accurate than the in-camera meter (which only does reflected) would have been.
You could also just swap to a Canon dSLR body, and use an F->EOS adapter ring, and you'd have accurate stop-down metering, but only aperture-ring aperture control (I've used a pre-AI Nikkor-SC 55/1.2 this way). But, given that you don't want to swap Nikon bodies, I don't think this would be practical. :D
