On the 1st day of cumming...jingle your bell!
Attach a bell to your cock or balls (string, tape; whatever works). Fap however you like, but make that bell ring with each stroke and listen to the naughty sound as you fap yourself to a satisfying orgasm!
When you're finished, be sure to hang or place the bell somewhere in your house as decoration until the entire 12 Cums of Xmas are over as a reminder of your Xmas fun! (If you got any cum on it, don't clean it off first either!)