I tried this in AA once and it worked, haven’t gotten the opportunity to try it again though.
The fact that arso now douses people who visit him is an underrated feature. If you are attacked at night, you can usually tell who did it unless they were already doused (in which case, it’s still possible to figure out via process of elimination, unless you have the majority of people doused). Unless you’re sure it’s vig, claim sheriff and say that your attacker is suspicious. Even if they accuse you on the stand, it’s likely town will think they’re being salty or trying to get you lynched to help their living teammates. If there’s a spy and they say you’re visited by mafia, you can call out the RM who visited you as sus. If you don’t want to call out evils straight up, you can fake an invest will with reasonable accuracy and use it to cast suspicion on evils later in the game to thin out the mafia. In coven, you could also use this same strategy with psychic or even tracker.
In ranked or RP, if you’re investigated, by that point everyone knows it’s an arso game and will probably just think you’re doused. In AA people would be more likely to think that you’re doused rather than arso faking TI, I think, but if another arsonist dies you can always say that you investigated them and that you must be doused.