Sorry, I was away and you've moved on to melting the holes now.
Here is a trick learned from an electrician who installed many ceiling fans for neat-freak customers.
Take an old basketball, cut it in half to make a huge cup, drill one hole in the center to match the diameter of your bit shaft, slip it over the thinner end of the drill bit before inserting the bit into the drill (cupped away from you). Done correctly, it looks like you are demented and think you are holding a ray gun.
Have some trusted person hold the already filled plastic pot over your head (Yes, dear...
) and drill away. The majority of the dirt/soil with be captured in the cup. If you don't happen to have an old basketball, this also works with large yogurt containers, etc.