First, before you do anything you should check if you even should do this. Modern peripherals may have local storage (for drivers and such) and they may be visible (even automounted) by the OS. In that case your risk profile may not allow it (see stuxnet). Also be aware that sharing one keyboard will make you prone of brainfarting and muscle memory your credentials from one PC to the other. Depending on the reason behind airgapping, that may or may not be frowned upon.

Anyway, I use a "dumb" version of this setup, out of convenience. I have a dumb USB switch, with only one host connector. I use 2 cables, and have them tied together with a binder paperclip thingy. On the (rare for me) occasion I need to switch, I just unplug one cable and plug the other.