For most normal bowels, the lower colon is typically empty. It is only full of shit when one is feeling the urge TO shit. Hence the advice to have the girl poop is a good one and as a result you won't be packing any fudge. If she can't take a dump it's because her colon is empty and so you're good to go!
If, in addition, she does an enema too, then so much the better.
but it is not absolutely necessary.
The advice for "lots of lube" is not universal, in fact too much lube can work its way up the bowels and end up causing an enema like reaction. So follow this advice on a case-by-case basis. I've had a several girls who preferred minimal lube (just their own pussy juices) and I've had friends who basically squirted a tube of KY up the girl's butt and then wondered where all the diarrhea was coming from!
The porn style "ass-to-mouth" routine requires that the girl not eat for 12 hours AND do an enema, in order to reduce the risk of transmitting E. Coli bacteria to the upper GI track (makes one puke like a mothafucka
), and don't take your cock out of her ass and stick it in her pussy either or you'll give her bacterial vaginosis and have to deal with a stinky pussy!