I'm just going to come right out and say this, in a large bolded font.
You do not need to rinse formula poop off of a diaper before you put it in the wetbag. There are no extra steps. It is just as easy as breastmilk poop- maybe even easier*.
I've been wanting to write this entry for a few days, and I've been having a hard time coming up with an introduction. How do I start this entry? Why am I even writing it? I'm writing it because 16 months ago, I was wishing that someone had. I had just made the decision to stop pumping for my 4 week old and switch to formula. Every single website that you find about cloth diapering tells you about how magical breastmilk poop is- it dissolves in water! You don't have to rinse the poop off! The diapers clean themselves! RAINBOWS! This was all fine and very reassuring to pregnant me, and pumping me. But when I decided that my lactating days were over, I realized that I had no idea what I was going to do re: poop.
I looked around, and I saw a few vague mentions of having to rinse the poop off beforehand, or scrape it off, but then the author would reassure you DON'T WORRY, BREASTMILK POOP WILL WASH RIGHT OUT! Honestly, it seemed to me like the cloth diapering community just doesn't acknowledge that parents who choose to formula feed are just as willing and capable to choose cloth diapers. Not cool. I made a post on Livejournal asking about what I was going to have to do when we made the switch (he was already getting maybe 3 bottles of formula per day) and a few women kindly told me that they didn't change anything. It is the same as breastmilk poop. They were right. My son's poop definitely got a whole lot smellier, and it looked different- thicker, mostly. But I didn't waste any time trying to remove the poop from the diaper before I washed it and just threw it all in the washing machine, and what do you know? It all washed out- just like the breastmilk poop did.
So, this post is for the pregnant woman who is not interested in breastfeeding at all and is going to feed her child formula right from the start. This post is for the mother who breastfed at first, but for whatever reason is choosing not to continue any more. This post is for someone who breastfeeds, but is trying to help a friend or relative who doesn't. It's ok to formula feed, and don't let anyone try to tell you that it will lead to more work with your cloth diapers. That is not true, not even a little bit. Every time that I see a post on a messageboard where someone is wondering about what to do with formula fed poop, I will always respond. I want to make this knowledge abundantly clear, because I wasn't able to find any of it when I needed it and I don't want anyone else to have to be stressed about it like I was.
* In my experience, that crazy yellow breastmilk poop stains like CRAZY. Formula poop, on the other hand, never left a stain on the diapers here. Your milage may vary ;)