-By rubbing the coin or bill on and around the prankster's ass after a hard bowel movement. The prankster would rub all of the shit off their ass with the coin/bill until it's coated with shit or at least until there's no more shit on his or her's ass.
-Forcing the coin or bill in the prankster's rectum before having a bowel movement, then forcing the shit down in the toilet, then manually finding the money in the pile of butt paste that is usually caused after shitting the money out.
Then after doing either of the above, the prankster would have to wipe off any remaining traces from the money, lest the prankster risk having the victim suspect anything. Later when the prankster gives his/her victim the money, he/she will be shocked and disgusted by the *awful smell of the money.
*smell may vary
(noun) Money that smells terrible, usually carrying the smell of shit.