Now I always thought the worse thing you can do to a car is to polish it every week as car polish is actually abrasive and will eventually damage the clear coat which causes the swirl marks. The recommendation is to polish a car just once a year.
I'm a bit obsessive with the cleaning thing & follow a very strict routine.
1) I wait until it has rained. It has to be a very gentle rain, more of a drizzle really & it has to have been ongoing for several hours. (N.B. This particular method of detailing doesn't work if the precipitation is any heavier.*) I find it really softens up the grime & makes removing it a doddle.
2) I get me bucket of warm water, sponge & bottle of Fairy Liquid & go outside to the car.
3) I start at the roof & wash from the top down, being careful to avoid cutting my hand or sponge on the rusty bits.
4) I finish & go inside for a cup of tea.
5) I let the rain rinse it off.
I do this at least once a year, though 2015 has been a bumper year & I have done it twice already.