I believe more important than just a coffee enema, it is necessary to change your life style. My own suggestions would be eating healthy food, taking necessary supplements, drinking adequate amounts of water, doing complete inner body cleansing on a regular basis.
When doing a bowel management, enemas and colonics could be part of the routine. Also the inner body cleansing should include liver flushes.
I think that all this would help your Acne problem. For a short answer to your question about taking a coffee enema, myself, I would take cleansing enemas followed by a coffee retention enema and I would do it daily for 3 to 5 days. See my Blog under “M” My challenge by ProPaul