Can you give us an idea of what you mean by slow blues?
I think - minor blues when I here Slow blues, Like this
Slow Blues If you have some specific tunes in mind, drop us a line and we may be able to hook you up. Not all Slow Blues follow that very formal I, IV, V - actually most don't.

I gave this a little more thought and have concluded that Slow Blues certainly does not have to be minor. Like any blues, the major /minor mix is really the trick. Or even a chord voicing which using only the root, b7, 5 and avoids stating the 3rd/b3rd can work in slow blues. Perhaps Slow Blues are simply just that - blues played Slow
Blues Played Slow