This Can Be Accomplished A Few Different Ways.
Probably Best Done In Classic Any/ All.
You Need Either A Transporter Or Another Arsonist To Net This Achievement.
- A Transporter Can Switch You And Your Target, Making You Douse Yourself.
- Another Arsonist Can Douse You When He Visits You, Or You Can Get Doused Visiting Him.
Easy Way
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If Someone Said They Are Transporter, Shoot Them A Whisper
- Tell Them You Want To Hit Yourself, "So Target Yourself And Me".
Organic Way
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The Any/All Playlist Is Your Best Bet, As You Can Get A Few Arsonists In The Same Game.
- Visit Around For a Few Nights Then Ignite, Repeat.
If You Are Pretty Sure You're Doused, Hit Ignite, And The Achievement Will Pop.
Good Luck!