I think she was wiped down right after the sexual assault. BEFORE she was redressed. BEFORE the urine release. It must be at least considered that she wiped down while still alive, though probably unconscious.
The sexual assault occurs first.
JBR was either naked from the waist down or had her panties and long johns pulled down for the sexual assault and wiping. Somewhere during this assault she screamed and was bashed on the head to silence her quickly.
That rendered her immediately unconscious and on the irreversible path to death.
Seeing there was no turning back at this point- the Rs now have a dead/dying child who may have been bleeding at this point from the vagina even before the paintbrush stab.
To cover this up, and without thinking about an autopsy and what it may reveal, they wipe her down, put clean panties and long johns. She voids her bladder upon death, but the small drops of blood that oozed into the new panties are not seen, because they do not undress her again, and the blood is not enough to show up on the long johns.
The Rs decide to leave her in the wet clothes, but they are now in a state of panic as to how to explain the death. There is no visible head wound. The fracture cannot be seen. They think she is dead (she may or may not have been at that point), and need to SHOW a method of death.
So they scramble to devise a makeshift (and non-operational) garrotte with materials at hand- the paint brush, cord and tape, all from PR's paint tote RIGHT THERE in the basement.
But though they pull it tight, unbeknownst to them the autopsy will show that it was not tight enough to damage the internal structures of the neck nor break the hyoid bone. By itself, it may not have even been enough to kill her. But they don't know that, nor do they know the extent of the skull fracture that will show up at autopsy. They also use the paintbrush handle to hide the sexual abuse.
Buy this time, the urine has dried enough not to wet the white blanket, which they took from the basement dryer (where it was always laundered every time she wet the bed). They wrap her, and place her in the wineceller, where the bits of fake greenery get into her hair, since that room was used to store artificial Christmas trees.
Then, they write the note, and anal-retentive PR REPLACES the pad and sharpie, NEVER thinking the ink would be tested or the paper would be traced back to the pad, and in their panic, never think about the practice note, since it says nothing incriminating and they never think about the handwriting matching it, as PR writes the note hurriedly and possible with her non-dominant hand. They possibly don't think about the house being searched. They never think the pad, practice note, sharpie will be taken into evidence along with the RN.
Then they make the 911 call- and it's showtime!
IMHO, if there had been VISIBLE head injury, (which would explain why she died) the garrotte would never have been made. They could have just as easily blamed the head bash alone on an intruder than to stage that strangulation. They'd still have wiped the flashlight and batteries down and said it wasn't theirs. Nothing would be different from the way it happened except there'd be no garotte, nor speculation about the cord and tape.