A long time ago when I was in college, I had done a lot of rebuilding of cars that were in fires and learned a lot about what works and what doesn't. Don't waste a lot of time trying to paint the sheet metal, because for some unknown reason, paint usually doesn't stick to the metal once it is in a fire. I would sandblast the sheet metal and use a etching primer on it. Then top coat and hope that the paint stays for a while. If it bubbles and lifts, then consider finding a replacement panel. The engine is usually not damaged, however all the accessories will have to be replaced. Plug all the holes and then power wash the engine with water only. If you need to degrease it, then use Arm & Hammer washing soda and dish washing liquid. Let the engine block get a surface coat of rust on it and then steel wool to clean. Brush or spray on engine paint and it should stick well. All the rest is just replacement of damaged parts and wiring. I prefer to buy new wiring whenever possible or if there is enough of the old, then you can carefully reconstruct the damaged parts. Usually buying new is easier and faster. Be careful reusing any old hardware that might have been heated. New hardware is cheap and don't forget to use never seize on all threads. It is a dirty job, but not a difficult one. Patience is what is needed and a lot of pictures to show how everything goes back together. I had only done one tractor and that was back in 1964, so I don't remember much about it.