When I wrote "barrel lenses" I meant vintage brass lenses that do not have a shutter mechanism or a focusing helicoid, but do have an aperture control mechanism.
1. The native Kiev lenses are also barrel lenses except that they have a focusing mechanism. If you want faster shutter speeds, you might be able to mount a Copal, Compur or Prontor 3, Shanel 5A or the larger Acme and Ilex shutters in front of the lens. You will of course have to ensure that there is no vignetting. The digital back is connected to this shutter.
It may be possible to mount lenses from other SLR cameras, as long as they can focus at infinity (or at portrait distances, if that is your priority).
2. Barrel lenses as used with large format cameras pose the additional challenge of focusing.
This can be done by mounting the lens in a helicoid like the Pentax 67 Helicoid Extension Tube. This will naturally add some extension, so you would be limited to using lenses longer than 105mm or so.
Again, if you can live with the 1/30 sync speed there's no need to do anything else. For faster speeds a front mounted shutter may be possible.
3. Using regular large format lenses mounted in shutters is straightforward. Mount the lens in a body cap, which in turn mounts in a focusing helicoid (like the Pentax) and connect its shutter to the digital back. Again, you are limited to 105mm and longer lenses.
In all these cases, you would keep the shutter on the camera body open at 1 second, B or T and trigger the back with the connection on the external shutter.
Shutters like the Sinar Copal and Packard would minimize vignetting, but they are very large.
Using Sinarbacks is certainly not as convenient as using a modern CFV100 back, but is certainly far, far cheaper. Sometimes cost is an insurmountable problem... There are still many commercial photographers still using them and making money.
Kumar