For the rest of us, to sibilate we need esses. Or zeds (I understand you call them zees in the USA). Or possibly cees. Use them liberally and with relish: cause nervous mongooses to dive for cracks in the pavement, and mothers to check if they've left the gas on.
She sells seashells by the seashore, I understand, in Mrs Smith's Fish Sauce Shop, though Sheila seldom sells shelled shrimps, but crisp snacks of salty squid.
Or, to go for a classier option:
Could trammel up the consequence and catch
With his surcease, success
Ah yes. Macbeth was a great one for sibilation -
To make society
The sweeter welcome, we will keep ourselves
Til suppertime alone.
The question that inevitably arises is, is sibilation a sign of a scoundrel?
Not necessarily. It might be a sign of badly-fitting false teeth. Or a semi-eaten gobstopper. Or a shyness or tenderness or sadness so acute the victim can only whisper.
And so, sadly, to this post's finish.
Parting is such sweet sorrow, isn't it.
Thing To Do Today: sibilate. The Latin word sīlbilāre means to hiss.
*In Jeeves and the Feudal Spirit.