Fence building question

[Emmerich]

Is there a gizmo that can *easily* be used to brace fence posts while concrete is hardening? Setting stakes and boards is a pain and I was wondering if there was some sort of device the pros use to do this. Being able to adjust them after staking would be ideal. I would think if such a device exists, it would need to be cheap because a pro would need to use several at the same time.

Fred