I have two hammer guns, without safeties. They work OK! for Quail or Pheasants over good dogs, but absolutely forget it for Grouse or Woodcock.
One can carry the gun with shells in the chambers and the action open with hammers cocked and then close the action when a bird flushes. But, talk about inconvenient and slightly dangerous.
Problem is, of course, that quality doubles, of any vintage, with hammers and safeties are mucho expensive.