I'll second that, ultrapac is really good for this type of work.Try to vac as much soot as possible before hand or you will be just moving it around for ages before it all comes off.Remember not to use the vac after on anything like a office clean ect as the hoover will smell of smoke for ages and so will the room you hoover in. Make sure the customer knows that you can not guarantee that the smell of smoke will go completely after cleaning, smoke can get into paint and i have even known were plaster has had to be taken off because the smell was still there months after, even after a deep clean and re-decorating!