With Future Floor Wax, the trick I've heard is to first mist it on and let that seal and then do a second spraying. The misting layer should protect the chrome paint from reacting to the solvents of the clear coat and thus turning grey.
Mind you, I have not had time to test it yet, but there were pictures shown off on endobuilders of someone having used this method and the results were promising from what I could tell.
I've been using Rust-oleum specialty metallic silver with great results, looks more like chrome than chrome paint
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