AOBP's (all over body poops) generally happen when you are away from home and forgot your diaper bag. They might not happen all the time, but you (or hopefully your husband) are pretty much guaranteed at least one. First, you need some tools, which you will not have, otherwise you would've avoided this in the first place.
Here is the list, and a list of substitutions in emergencies:
Wipes or Napkins, your socks , running water (nearby stream or gas station faucet)
Trash Bag or Route 44 cup, pickup bed, folded map or magazine
Changing Pad or Blanket, adult shirt, your legs (if you're in an airplane)
New Diaper or Paper towel lined grocery bag, your shirt
New clothes or (only necessary if it's cold) anything of yours
Ideally you have taken a course on contamination isolation, like if you worked at a nuclear lab. If not remember that as soon as a contaminated article touches another, that article is contaminated as well. If you discovered the AOBP, most likely you are already contaminated and it is your job to clean it up. So, take a deep breath (jk), relax, and make a space for all contaminated articles, and just do it.
Try to remove the babies clothing without spreading the poop. You can roll her onesie over the poop all over her back so it wipes up and the clean part of the shirt is what touches the back of her head when you pull it off. Do not pull the onesie over her face. Any clean clothes (maybe socks) can be set aside and used as wipes if necessary. Wipe off whatever poop left and push the wipes down her back into her diaper. As you undo the diaper, slide any clean parts down across the skin to absorb any poop. Now, roll up the diaper and use the sticky tabs to close it. If possible, carry baby to running water and use your already-dirty hands as sponges, making sure your contaminated pile is safe from other babies or animals while you're gone. Redress baby and hand it off. Then, dispose of contaminated paper items, and launder clothing.