For the first couple of washes I used a bucket of water with a small amount of washing up liquid and a sponge.
Current method I use is to spray the car with a hose, followed by using a washing mitt with a bucket of water mixed with some kind of cleaning product (partner's car came with some Diamondbrite shampoo so that's my current choice). Then dry with a large microfibre towel. That's enough for me.
If I can't be particularly bothered, just squirt the hose at it for a bit to get rid of some dirt and mud.