I have never gotten this close. The blog from Austin Adams is the way to go, I just interpreted it wrongly.
On Debian Stretch, I have it almost completely working.
It is extremely easy to setup(!) but it involves one crazy magical script which doesn’t seem to work well on Debian Stretch. I have therefore created a topic on the OpenVPN forum, also explaining the exact steps to take.
I am sure you will be shocked how easy it is 
Now hoping someone can fix the script for Debian Stretch.