I am not sure if this is the right place to post this, but, I started doing a restore on a "Every-Ready" or "Ready Set", can't recall the name right now, shaving brush. I cut and drilled some of the hair out but am finding it difficult to be accurate as I don't have a lathe. I am doing things countertop with drill bits and dremel.

Since my goal is not to destroy this handle, I am trying to find if someone could help me finish the job. I know I still need to buy a knot, but of course, I am not sure how big the hole is as I don't have a metric ruler laying around.
I will try to post some pics later.

Thank you in advance for your help, and I apologize if this isn't the proper place or decorum for this posting.