Tested on ~20 Samsung Tab 4 8.0 (SM-T330NU) running 4.4.2 but unfortunately no other devices.
If the tablet already has the extremely extremely obnoxious Samsung demo mode you'll need to do a factory reset. Go to Samsung demo settings from the notification tray, first password is 5444
, admin password to factory reset is M729Q16K8546
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Enable Development options by going to Settings -> General -> About device and tapping on the Build number ~8 times. When development options appear enable USB debugging (Stay awake is also a option to enable for a kiosk.)
Install Towelroot, launch it and click the magic button. You now have root and can uninstall Towelroot. This will allow us to completey remove the top bar later.