1) Take a look at Packard shutters.(posted 8768 days ago)http://www.hubphoto.com/ packardshutters.htm
I have never used one myself but the website explains a lot. Apparently they fit in front of or behind of the lens.
2)I have taken a few "portrait" type pictures with 4x5 camera and availible light with shutter on "b" so I know it's not convenient but it can be done. You are limited in the types of poses you can ask your subject to assume, but when I look at the work of some 19th century portraitists, I don't see this as a liability...
August Sander worked for most of or all of his life with barrel lenses, no polaroid and film with an ei of 12 or so and his pictures are fantastic.