Arrghhh!! bIII diminished seventh - what do I play?????

www.christianmillerguitar.com
In which I once again fail to make a 10 minute video.
This chord turns up in so many Gypsy Jazz and Swing standards it's just not funny, and yet info on it is thin on the ground. Here's an attempt to rectify that a little...
Handouts will be issued - watch this space