[Catbird]

Here's an old hot rodder's trick that seems to be working well for me:

Each time I pull the lower cowling off for any reason, I coat the entire exhaust system from the exhaust ports at the cylinders to the end of the tail pipe with automatic transmission fluid, including the muffler and springs. An old shop rag works well to smear a liberal coating of the stuff. Leave it wet, but not dripping.

When the engine is fired up and the exhaust system comes up to temperature, the automatic transmission fluid just seems to go away, leaving a gorgeous burnished copper/brown finish on the entire system. No surface rust.

 

[Sid Lambert]

Automatic transmission fluid has a flash point lower than some exhaust temps. I'd be careful if you do this.

 

[RFSchaller]

Since only about 6" of the exhaust stick out and it's below the cowl mostly out of sight I don't see the aesthetic value. Since it's stainless you don't really gain any corrosion resistance, so I don't see a big advantage that would justify a potential fire hazard on the first start up.