Cleaning Exhaust Manifold

[danz]

Hey guys, I took my car for a test drive straight after my turbo conversion without the heatshields on, I got some bad luck and a tranny cooler line blew off and the fluid spilt everywhere and caught on fire on the hot exhaust manifold. I ended up using the fire extinguisher, but now all that fire extinguisher dust is stuck on the manifold and wont come off with degreaser and high pressure cleaning. When I drive the dust starts cooking on the manifold and I need advice if its possible to wash off?

cheers