Like for me a example of expansion would be this male inflation scene with a firehose in the butt from wrong turn six it was a crazy dang scene remember it really scaring the crap out of me at first basically killer hillbillies want to turn dude into a parade balloon. They're first attempt? Shoving a hose into his mouth only to realize it wouldn't work so attempt 2 if you can't go though the front go through the rear as they pull down his pants and jam it up his pooper! It's then it finally starts working and his belly starts expanding til well baboom!
Crazy scene from start to end haven't really scene one like it since.
As for my dream idea for a inflation scenario like I've said previously I feel like when it comes to killer clowns there certain expectations to hold. Clowns and balloons seam to go hand and hand with most media (like look at pennywise and rocking both a pile of red balloons and a balloon shaped head!) So idea wise random 20 something girl, motive could be anything really! Maybe she has big tits some people call her balloon bitch? Maybe she's a bit clueless so people call her airhead.
So clown goes after her uses whatever is laying around junk was is usually how horror films do these kinds of kills expecially if the kill is motivated in randomness vs. planned.
After disorienting her
Grabs the most random bike pump hose or slams her mouth face first into a old helium tank and let the inflation being.
Bike pump would be slow either belly expansion or again get a squeak latex style TMC suit and well pump it up under her clothes for full body inflation effect leading to desired effect which whether it be breast expansion, Belly expansion, or full body squeak latex goodness the desired effect is the same bang/death. Cue Next movie scene
The idea being the clown being punny by ironically killing her with a tactic that she's been called her whole life or at least the whole movie.