CVT Brushes

I've taken out the Carbon brushes on my k11 and it's no wonder that the thing was having problems as they'd worn down completely to the holder! The brushes I took out were covered with oil and carbon 'dust'. Is that normal? The reason I ask is because the second hand unit I have put in was spotlessly clean - might be that the breakers cleaned it up - but it was spotless! So does anyone know? Should there be some lubrication where the brushes come into contact?
Cheers for any info.
No lubrication needed. Brushes are designed to wear down.

So where's the oil that was all over the brushes I took out come from? Could it be caused by there being too much Automatic Transmission Fluid put in? (just been serviced and the levels seem quite high).

Thanks for any comments that could shed some light on my mechanical darkness!