The only time I decided to use coffee based developer, I used coffee which had been brewed and the remainder left in th pot for a few hours. You know, that stuff that smells so strong youthrow it away and brew fresh.
I did this prior to reading anything about using Folgers, or any other instant crystals. Also, I had not read much about ascorbic acid. As a result, I just simply added some carbonate to the coffee and developed a couple of sheets of HP5+ by inspection for 25 minutes. The resulting negatives were tanned, thin and very easily printable. subjects in deep shade were hardly visible on the negatives, but printed well. They made excellent prints with palladium.
Perhaps it is time I tried adding ascorbic acid to speed up the process.