(YS 252) "...this places a temporary aspect on a target or the scene, or removes a temporary aspect from a target of from the scene."
Same page says that "by default, pulling off most maneuvers requires 3 shifts of power" and goes on to discuss how it is frequently harder to affect characters. Since those same 3 shifts would be enough to light someone up with a Weapon:3 attack, I'd say a caster is already pumping a substantial amount of mojo into it. That's the same amount of energy as a Desert Eagle or other absurdly large hand gun, more than enough to light up a scene.
As for putting out a fire, I'd personally require the caster to use shifts equal to the fire's intensity. If the fire is simply an aspect then it's a three shift maneuver. If it's counting as a hazard and doing damage, then I'd make them pay 1 shift for each 1 point of damage the fire does, plus 2 per zone affected.