Soot is the black film a fire leaves on surfaces that did not burn through. On a wall it looks like dirt. On a cloth it comes off as a smear. That smear is the mistake people make in the first hour.
Dry soot sits on top of paint, tile, glass and sealed timber. A dry cloth or a wet sponge drives it into the surface. After that, the wall needs more work than it did when the film was still loose. Leave it. Photograph it if you can do that without touching it.
Ceilings, cornices, the top of door frames, inside cupboards, on appliances, and on plastic blinds. In a roof space it settles on insulation and timbers. A room that looks wiped at eye level often still has a band of soot above the picture rail.
We clean what can be cleaned and we say when a surface will not come back. Call 0435 118 851 and name the suburb. If the fire also left the place wet, read water from firefighting as well. Soot and water together are a different job from soot alone.
A household vacuum blows fine soot back into the room. Do not.
No. Many marks are film, not char. Char that has burned the plaster is a different decision, made after a look, not from a photo alone.