Quote Originally Posted by BlueWind
Older cameras seldom have shutters with slow speeds (I mean speeds between secs to 1 or 2 secs)
Which older cameras? You mean from the 19th century? All of my oldest cameras (pre-War models dating from before 1926 to 1935) have Compur shutters with timed speeds down to 1 second. Anything longer than that, I can easily do with a cable release, and 1/2 isn't hard. Timing 1/4 with a cable release is a little tricky, but if you shoot two, it's very likely one will be within a half stop (after a little practice with a stop watch, that is).

Trying to get another shutter to control the one that doesn't have the speeds you want seems a major violation of the KISS principle, and likely to cause one to run afoul of the Murphy police (they're the folks who make sure that whatever can go wrong, will, and at the worst possible time).