Technical Model A hydraulic Brake Conversion- Rear

Hey there. I am about to attempt this for myself. Now I have read the following site as well as many posts here on the HAMB.

RELATED:
http://www.lainefamily.com/ModelAFiles/ModelABrakeUpgrade.htm
http://www.jalopyjournal.com/forum/...ting-39-48-hydraulic-brakes-to-your-a.124112/


Now, I just wish I knew what he used to make the intricate cut seen in this video.


My set up: (Four posts down from top or so)
http://www.jalopyjournal.com/forum/threads/1930-ford-coupe-project.954246/page-6


-I do not have access to a machine shop, and have not found one to do non-business work yet.
-I do not really like the cutting method as I believe; especially up here in new england, that the open space is just begging for salt, water, and dust.
-People do not like the full flip as the bleeder is in a location that can be hit by debris.

What is the best way?

 

I did the flip method on my A in the early 60's worked fine, bled fine.

 

What did you use to make the crescent cut?