Deburring steel prongs on RV-10 firewall

What have people used to debur the holes you drill through the prongs? I'm thinking a dremel and then a small wheel if I can fit it in there but I'm just curious if there is an easier way I'm not thinking of. Thanks

Nick

A much larger drill bit, spun by hand (wear gloves).

Similar to Bob's idea------step drill.

I used a step drill for all holes I put in the firewall, then go to the back side and clean up the burr with the same drill, using the next size step.

Quick and easy.

A bigger drill bit and a step bit won't fit in where I'm talking about. The prongs make a "C" shape in all four corners and its only 1.5 inches wide. The holes straight in I can get but the top and bottom row have little room to get to the hole from the back side.