I don't use decaf coffee for any purpose. I want coffee for the caffeine kick!
I also would not use instant coffee, since I would be wary of what chemicals were used to make it "instant."
I don't buy fancy organic coffee either. Cafe Bustelo is cheap and available at most fine grocers near you. There are a few others: All in the general class of "Cafe El Cheapo"! (A few are espresso, if you like the extra caffeine kick.)
Lets face it: yer gonna squirt this stuff up yer butt then squirt the results down a toilette. You really don't need $39.95 per pound organic, special made for enemas, coffee for that! (IMHO!) (But if you like it and can afford it...enjoy!)
I usually make a full 10 cups in my coffee maker and add cooler water to make 6 quarts of a moderate temperature. If I really plan to hold it for a long time I only use 4 quarts 'cause I can comfortably hold that volume a long time (15-20 minutes.) (I can hold 6 quarts too, but that gets really unpleasant.)
I have a plastic basket in my coffee maker since I read that the filter papers filter out a chemical in the coffee that helps detox the liver. I've heard it's better if you have a metal, screen basket.
Some folks insist on filtered water. But since I use 6 quarts at a time and maybe 6 enemas in a series, filtering 36 quarts of water is tedious. But I agree it is probably better to use filtered water.
I also read somewhere, that holding a coffee enema for longer than 10 minutes defeats the purpose, since the liver empties toxins at first, then starts to re-absorb them after 10 minutes.
There are all sorts of people with different "science" on this, including those who insist the "science" is all hokum.
Some people use very elaborate recipes: I think they are into the ritual of their recipes. Though different recipes will have different effects on your "outcome"! 😁