Never owned a bike nice enough to seriously worry about the paint to the point where I feel the need to wax it though that may change with the recently completed Klein Quantum II project.
That aside, I've long been using a damp rag, preferably a microfiber, to get the frame, fork, wheels, etc, looking clean. I'll shake out and rinse the rag a few times to get the grit out. Then I'll use a regular shop rag on the components. If I rode through some seriously wet and nasty conditions, the whole bike gets hit with the air compressor first when I get home. Really helps ensure all the water has been pushed out of everything. Sometimes I'll feel the need to pull the seatpost and flip the bike upside down to let any water in the frame drain but that's only after riding in the rain or taking the mountain bike out in especially bad conditions, something I actively try to avoid.