Extinguishing player with waterballoon makes him flamable entity that can smolder. Not sure how it works with ice staves. Didn't check if that buggy flag-change makes player extinguishable by ice flingomatics too (they don't affect players by default).
Its kinda a thing since solo rushing dfly with waterballoons becomes kinda tricky. Every magma pool becomes your enemy and you are very likely to get burned by lavaes (even if you kill them - you will start smoldering and burning...)
Set yourself ablaze via magma pool or lavae. Extinguish yourself using waterballoons(gotta check how it works with ice staff though). Now any open source of fire will make you smolder -> will set you on fire after a few seconds.