[Fullraceflathead]

That process is called arcing the brake shoes. It is still done today but on larger semi trucks. It's very hard to find a brake shoe arching machine in today's world as they actually outlawed them back when they were using asbestos for brake shoes. Today asbestos is no longer used but the arching machines are few and far between now. Large semi truck repair shops still arc brake shoes. I actually own one Ammco machine. They are around and if you contact a Model A club most likely one of the members has one of those brake shoe arcing machines.
You can also put self adhesive sand paper on the inside of your brake drum and sand your brake shoes until you see a full contact pattern on your brake shoes. Modern brake shoes are not made from asbestos. I would not try this with older unknown brake shoes just to be safe though.