Using a lens without a shutter is fairly common with view cameras, especially for 8x10 and larger. And, of course, most of those using very old lenses don't have shutters. What you need is a hat, or at least a not too tightly fitting lens cap. It's common for exposures to run 1 second or longer, and with practice you can be fairly accurate just taking the cover off (lens cap, hat, whatever) and then replacing it after the requisite time. It's a simple, elegant solution that works better than you might suppose.