It all depends on what is expected. If I have a couple of litres of psyllium husk gel inside me, the toilet is not a good place to expel - it will block up. First of all, I have to get a long colon tube or similar about 600 mm up me or I can't get anything out at all. The best place for this is squatting in the shower. With the water running in the tube, I ease it up alongside the object inside me, which is all one piece. It lubricates as it goes, and runs up the colon wall until its end is above the mass. Then I bear down gently and the mass inside me makes a seal with the colon wall and the tube, trapping the water in the cavity above the mass. The pressure rises and at a certain point of delicious distension, the mass begins to move. It's rather like the launching of a ship! What comes out is so big that I shan't attempt to describe it; and photographing it would be in poor taste! It then has to be broken up into pieces small enough to go down the toiet.
I have described expelling on the beach elsewhere: usually standing, bent well over, feet apart. The stance stops most of the muck from running down my legs; but if it does, it's really no problem to walk into the sea and wash it off. The bending definitely helps get the rectum and colon aligned, and it also helps get the farts out because they don't have to be forced to go downhill!
For general expelling (like last night) I prefer to squat over a small (10 litre) bucket. Mine is translucent plastic, and is graduated in litres. This enables me to see how much comes out of me, for correlation with how much enema went in. And it permits a good squat that promotes rapid expulsion.
For a really weird feeling, I fill with plain water, then work just the barrel of my semi-solid pump (see 'Bespoke Equipment' in the Gallery) up me and pump it up to retain itself. This is, in effect, a hollow butt plug with an inside diameter of around 42 mm (1.65") and water just pours out of it. I stand in the shower to expel. The inner end of the barrel goes right into the descending colon, so I can't feel any fullness in the rectum. I leak without any possibility of control! And if I squat, the leak becomes a torrent.
For the greatest possible comfort in expelling, lying on my side in a warm bath has no equal; but it is messy. Nevertheless, this position plus the warm water almost eliminates cramps. It's amazing.
Johnny