[morzh]

I never bothered too much about it. However I don't think you need to keep those lugs in the firts place. You won't be able to make the case the common nebgative again so you will have to drill another hole and thread the common negative wire through it. In the same fashion you can drill out the lugs and thread three wires through and then connect them to the caps' leads. Then you could care less about the resistance.

If you still want the lugs used, just moat each lug instead of trying to clean the whole thing.