Washing Rick Steves Bags

As with all soft luggage, you cannot put it in the washing machine.

Turn the bag inside out and use a sponge and gentle soap to wash the interior.

You can do the same for the outside, you might try a soft brush to get into the fabric texture, but dirt is just part of the game. The fabric may hold onto most of the dirt/grease. Once used, your bag will never look brand new again.

Take pride in your dirt! It proves you've used your bag for travels.

I have taken my soft luggage to the drycleaner in the past. Apparently they have some sort of special process for luggage and Sports Bags.

I have not done this with the RSCC so I haven't any idea as to how it might turn out.

The method described above sounds reasonable. I've done that on occaision using Woolite. I also re-applied rain repellant at the same time in case I washed it off.
If it's just stinky and not too dirty, I spray a little Fabreeze. Or make my own cheap and cheerful solution using diluted Fabric Softener in a spray bottle.

You can also use a Tide stick on the stains. It works great on fresh stains, not sure about older ones.

I agree on proudly carrying used/dirty luggage (althouth my bag looks nearly new after five plus years). If nothing else, you look like less of a rich American target for pickpockets.