If you can not clear/reach places, the best is to seal it in.* You can seal using foam, ceiling texture, foam and or/paint.* We had a small fire in the office and all they used as a bug sprayer pump can and soap water, and a ton of absorbent pads.* Then they re tortured the ceiling and painted primed the walls.* Most of the hard surfaces that did not abosorb the smoke and soot whipped clean.*
*
We bought a condo, but never moved off the boat, because of my ex wife and keep peace with my present wife.* Long story.* It looked like it had a small fire as the wall/ceiling/floor where dirty/grey, so we bought it for less and 50% of its value.* Hired a friend of a friend, gutted the entire condo, nothing was left but the bare walls and bath tub, washed down what we could, tapped the windows, doors, rented a paint spray and sprayed 30 gallons of primer sealing every thing including both of us.