Turbine soot master from real clean products.

https://www.realcleanproducts.com/index.php/detailing-products/turbine-soot-master.html

I bought it to use on turbine soot and it works even better on piston exhaust.  Spray on, wipe off, and safe for aircraft paint.  I used to use carbon X and usually had to apply 2-3 times to get all the soot off.  Now, it's just one pass, then I follow up with a spray on wax/coating.  Real clean also makes a speed wax which goes on/off really easy and lasts long with a great shine.  I use the soot master to clean most things on the plane now.  If you are a member of the beech talk forums they have a discount code as well.  Just search around the forum.

No, I don't work for real clean just love their products.  I buy soot master by the gallon.  My only complaint is that their spray bottles are kind of delicate and will crack easily at the top thread if dropped.

Luke Alcorn
N72231