Well, if you want to test a pose, you'd probably want to create a dummy animation first, have autokey activated, and edit the weights from there.
If I want to test how a mesh will deform, I create an animation where the bones to which it will be binded move, I play it, then while it's playing I adjust the weights.
If I need to add some more bones or I notice I didn't place them right, I unbind the bone in setup mode, move it, (because otherwise the mesh gets a little wrecked) then I re-bind the bone to the mesh.
You could give this method a try (: