My car wash technique is the two bucket method and lambs wool mitt!
Rinse car first, one bucket has your car wash in, the other is a bucket of clean water. Dip the wash mitt in the soap bucket,wash a panel or section of car then rinse the mitt in the bucket of clean water. Then back to the soap bucket and repeat. The clean water bucket rinses the grit and crap off the mitt and ensures you are washing the vehicle with clean soapy water.
Rinse off once finished then dry with a microfiber towel or two.
Claying the car is a very lengthy process (for a vehicle of the Cali size) and must be followed by applying a good quality wax to protect the paintwork. The easiest way to tell if paintwork needs to be clayed; when the paint work is clean, run your finger over the paintwork, it should feel like glass with a smooth clean feel. If it feels a bit rough or gritty (even though it looks clean) then Claying will be of benefit.
There are various grades of clay depending on how bad the paintwork is, the stuff you buy from halfords (mcguires quick clay) is good stuff and fairly mild. If you do use it, makes sure you keep the clay/panel being cleaned wet with the supplied spray and keep turning the clay to ensure you always use a clean side. As you clay the car you'll see the dirt coming off on the clay.
Once it's been clayed and waxed any water droplets should roll off the paintwork, it will look great and it's surprising how 'dirty' paintwork can actually be with microscopic dirt and contaminants.
I buy my car cleaning products from http://www.polishedbliss.co.uk
they have a very good website including lots of 'how to' tutorials.
For those of you with OCD you can waste loads of time looking through their tips, products etc. I have also found them excellent in providing advise for specific products for specific colours or finishes of paintwork; give them a call or email them and they are usually happy to help. For example, our metallic grey mini has a 'wet' look once polished that brings out the metallic fleck in the paintwork. This is achieved by applying a gloss polish before applying wax. Only needs doing about once or twice a year, but looks amazing after its been done. The guys at polished bliss can advise various types of 'finish' to suit your Cali colour!
All the products I have purchased from them have been easy to apply and easy to remove/polish off, no issues with polish drying and leaving nasty white powdery residue. Some of the products are not cheap, but you get what you pay for.
I have no link or affiliation with his company other than to have used their advice and purchased their products both of which I have found to be excellent, so I am more than happy to recommend them.
PS - "303 Aerospace Protectant" is amazing stuff for cleaning protecting and making any plastic trims inside and out sparkle like new!