Originally Posted by whoosh
I'm more concerned with cleaning the cassette and rear derailleur area. I can just wipe the chain down with a rag and oil it, right? Won't high pressure steam/water create rust? There's no way to dry in btw. those gear and derailleur crevices.
Cleaning the cassette and RD are actually a lot less important than cleaning the chain. Chain wear is GREATLY worsened by dirt in the chain, and cassette wear is greatly worsened by chain wear. That's why it's important to clean the chain with a solvent that will hopefully dissolve and flush out dirt-filled lubricant. You should read Sheldon Brown's article on chain wear:
www.sheldonbrown.com/chain
The rear derailer will last many chains and cassettes (barring some accident) and doesn't usually need much more than a cleaning and a touch of lube on the pivots. All but the crummiest rear derailers are mostly aluminum and not prone to serious rust.