well, yes and no. The flash will be full power, since it can't detect the aperture settings. That means you'll need poor lighting, low iso, 180 shutter speed (the highest you can go with a manual lens), and probably higher F-stop. In other words, you'll be doing a bit of trial and error.
I've only been using dslrs for a few months now, so I can only give you my experience, not necessarily best practice or even good practice
That said, here's how I use my manual lenses with flash, the few times I do.
Set the aperture i WANT to use, iso 100 (k200d), and crank the shutter to 180. Take a shot, and adjust aperture from there. Sometimes it's under exposed and I can reduce the shutter speed or raise the iso, but that's usually not the case, and I end up with a higher Fstop
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Actually, you can try and diffuse the flash some too, if the shot you're trying to take requires less exposure. I've even used the white body cap that came with the camera over the flash - it reduced the intensity an adequate amount and kept a nice even distribution, AND it held itself on up to a certain angle
YMMV
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Try asking your question as a new thread, either in the beginners corner, or in the DSLR discussion - otherwise the only people likely to see this question are those of us that were already in the thread, and not even everyone, since some have probably unsubscribed from it. good luck!