I pooped while pushing all three of my babies out and only one was caster oil.
I am not in your DDC but my youngest dd was born with the help of caster oil.This page
helped me a ton when I was deciding wither or not to use it.
It worked for me. I mixed it with ice cream AND root beer. It did not take 6 hours either. It was very quick. about 2 hours if I remember right.
Her birth story was published in a wonderful book. Here it is
if you want to read it. (page 217)
I did feel a little bit sit to the stomach but it passed quickly.
Just make sure that you drink water EVERY single time you poo (it will be a lot)