How do you finish the jimping after heat treat?

[PMQ]

I've seen a lot of guys use checkering file to make jimpings, this must be done before the heat treat. How do you finish the grooves of the jimping after heat treat? I don't think using a checkering file on hardened steel is a good idea.

 

[SS369]

I have been using abrasive cords and wrapping abrasive paper around a suitably sized backer.