BTW, if you use a hose, be sure it is LOW pressure! This has nothing to do with the frame but the BB, wheels, etc. No high pressure washing of any bicycle!

I either use a wet rag, sponge, or some auto soap (very diluted). I use a sponge made for nonstick pans on the (aluminum) rims and tires. I follow with Pedro's bike lust if I'm feeling like giving it a good shine (with microfiber cloth). This also helps subsequent dirt wipe off better. Do not use it on your saddle! Or handlebars! Bartape gets a good scrub with mild everything free dish soap. I rarely have access to a hose, since I live in an apartment, but when I do, that's when I tend to get the cassette the cleanest.

Don't worry about the frame that much. Treat it delicately and use a rack that is rubbery on the contact points. This goes for any bike really as you don't want to scratch the paint. It will have a good amount of paint on there. If you get a scratch so deep that you have scratched the carbon, then that was one heck of an impact, and you need to be sure the scratch is just cosmetic and not affecting the carbon weave. For mild scratches, a little bit of clear fingernail polish will do the trick and protect the frame.

I think the most important stuff to watch for with carbon is not cleaning it. I mean, would you take a wire brush to your painted metal car? No. So don't do that to any painted bike, aluminum, steel, or carbon. Treat it like your car's finish. Instead, watch out for torque limits on things like the seatpost, as it's easier to overtorque carbon than aluminum. Even if your seatpost is aluminum, the collar clamps onto the carbon frame.

Scratches won't kill your bike. Cracks will. There's a huge difference, and I can't imagine what you'd do to crack a frame while washing it. Still, you don't want to be scouring it. Nor will you need to. If it's caked from wet conditions, let it dry, then dust off. If there's sticky stuff, use a wet paper towel or sponge and maybe a little soap.