Read somewhere about the reamer being 7mm... so I just used a 6mm drill bit with grease in the flutes. Twisted around by finger while hunting around until it bottomed out. All 4 plug holes (240D) produced plenty of little black chips, and thankfully, no metal.

May not be the safest thing to do, but when I halfass something, I try to err on the side of less effective vs. causing trauma.