activated charcoal - best use and loss of product?

[Shattered_Symmetry]

I was wondering if anyone might be able to tell me what the best way is to use activated charcoal without losing too much freebase. I have read that it will clean the product up but too much will eat the spice also.

Is there a charcoal/spice weight ratio that anyone could suggest? also in the best case scenario what kinds of losses could be expected?

oh and am i correct in thinking it is added to the Re-x?