When Spike has a poopy diaper and he's managed to drop his payload OFF the rice paper liner, giving me a clean-up job, here's what I do:
Get the kid squared away in his fresh diaper and get him settled somewhere safe.
Get off as much of the poo as I can from the diaper using the paper liner or TP.
Grab the small white 3-gallon bucket (may be a 2-gallon -- we bought it at The Home Despot to use when washing the cars) from beside the tub, fill it about a fifth full with water, dump in the dirty dipe and add a little All Free & Clear (I keep a spare bottle beside the tub too).
Let the dipe soak for a while ("a while" depending on how long I forget about it soaking, the time between one messy poopy diaper and the next or the time between the soaking poopy diaper and wash day).
Check back on the diaper and use the old-fashioned "rub the cloth together to rub out stains" method. Wring out dipe and dump water in bucket down the toilet.
If the dipe is still somewhat stained, I'll refill the bucket with soap and water and let it soak a little longer. If the stains are gone, I take the wrung-out dipe and toss it in our dry pail (a Safety First "Odor-Less" pail for disposable diapers I converted into a cloth diaper pail with the help of a $3 waterproof bag I found in the sporting goods section of Wally World) with the peed-upon dipes to wait for wash day.
Probably not the best method in the world, but it works for me. Of course, we have a "spare" bathroom in which that cats' poo-poo box resides, so washing our human kid's poopy diapers in there seemed natural.