I would keep the usually as Cum swap is the only way to tag the very rare vagina to vagina cum swap or scenarios where the cum is pushed out or leaks out onto another, felching is a great addition but keeping this one a little vague gives more freedom.
"Depicts two or more characters exchanging already ejaculated semen directly between mouths"
I would delete the middle "usually" part. What other scenario would be a cum swap?
By the way, felching [1] is proposed and would constitute cum exchanged from anus or vagina to mouth. More clarification in [2]
[1] createtagfelching+33
[2] createtagsnowballingwithdrawn