We us 'go pee' for pee, and 'get busy' for poo.
We use the words as soon as we see Bo getting ready to do either. We are quiet while she does it, and then praise when she's done.
Giving the pup a word for their business is also helpful when you're on the road for a longer period, or at someone else's house. You go out - tell them their word, and they're more likely to go on command, rather than having to haul around a highway parking lot or a busy unknown area for 45 minutes waiting for them to get on with it.