Yeah for poop! Glad to hear she is starting to go again. Social animals need to be physically stimulated, not just to go to the bathroom, but to survive. This is especially true when you only have one baby (no siblings to pile together with or bump into. You will want to gently handle and stroke him or her between feedings. Using a soft bristled toothbrush mimics Mom's tongue.
You could also place a clock that ticks wrapped in something soft in the cage to mimic a heartbeat (they have commercial products that do this as well).
This is an Orphan Kitten Bottle Feeders and Fosters Facebook group that is very active and knowledgeable if you need more support. https://www.facebook.com/groups/652342198193392/
Good luck!
#FosteringaPet