This sounds nasty (and it is), but the best thing I have found for removing poop of that consistency from a diaper is to let it SIT. I used to work at a daycare when I had my oldest. I was able to use cloth diapers with her, but obviously I couldn't spray, dunk, or otherwise deal with the poopies until I got home. So her dirty diapers would sit in their zippered Happy Tushies wetbag until I got home... At which point the whole bag often got tossed into the diaper pail to await washing the next day. By the time I pulled everything out for washing, the poop had firmed into a mostly solid peel-able (please don't vomit) substance. I would just gently peel the poop off, throw all the diapers into the washer, run a rinse cycle, and then wash on hot. We never had any issues with our diapers or our washing machine.
to you, though. I hate that transition too. BF poop is so incredibly awesome compared to "real" poop. I remember when I was still EBFing my youngest, I ended up watching her age-mate cousin one day. The cousin was on formula... but I didn't think anything of it. I was just glad to get to CD another baby for funsies! What an idiot I was. As soon as I changed that baby into cloth, she promptly pooped all in it. I nearly vomited. I was NOT prepared for that (even after dealing with my oldest child's poop, as well as working as an infant care-giver in a daycare for quite a long time). I bagged that dang prefold up and set it in the bathroom... and promptly forgot about it. Needless to say, when I rediscovered that horrendous mess later-- the diaper got tossed. That's the only cloth diaper I've ever thrown away. LOL.
I will say that if my ever-so-appealing method doesn't work for you, I hear that a great many people have luck with diaper sprayers. There are contraptions that can help with the over-spray issue. I think Green Mountain Diapers website sold one... or had info on one... or I could be mistaken altogether... But essentially it's a big bucket with a hole cut out in the bottom or something. I'm sure a Google search would serve me well, I'm just lazy right now. LOL.