EDIT: Since it's been too long bbswitch = Bumblebee (which NVIDIA actually helps also) the open source implementation of prime, both of which also support the older Optimus laptops but ymmv with BB.

Also it looks like PRIME supports synchronization now if you have a distro with DRM support (no not the bad kind ;) https://devtalk.nvidia.com/default/topic/957814/prime-and-pr... so if you are using their currently suggested setup you don't need to switch manually anymore.