A brand new aircraft from the production line is coated with a lime green temporary protective coating (at Boeing anyway) before moving on to the paint hangar. The TPC is then removed with sand and a solvent is applied to clean the surfaces and after that water sprayed to aid inspection. Finally windows, radomes and other items are masked, so that they will not be painted.
The first stage is to apply a coat of chromate-based primer. To avoid contaminating the atmosphere, the hangar doors are kept closed during the entire painting process that can take up to four days. The paint is then applied next. The paint used is polyurethane enamel and is required to expand and contract as the aircraft is pressurised and depressurised during its flight cycles. Usually three top coats are applied. A 747 in multiple colours can use up to about 600 litres of paint. The weight of the paint varies according to colour and would you believe the heaviest is white. Boeing offer their customers 100 different shades of white. 40% of the weight of the paint evaporates during the curing process, which takes about 4 hours - steam both heating and curing the paint - which actually dries faster with humidity which is set at 30 - 40% during the process. After the paint has been applied and is ready for curing, the temperature in the hangar is raised to around 50 degrees Centigrade. After the process is complete it takes half an hour for the return to ambient temperature.
With regard to stripping paint from an aircraft, various methods have been used, but these days the methods have to be environmentally friendly and care must be taken to ensure that waste is collected for proper disposal. Lufthansa, for instance experimented with the use of frozen carbon dioxide, wheat starch and laser techniques before concluding that a mixture of water, alcohol and 7 to 10% formic acid is the most environmentally friendly method.
These days an electrostatic painting process is used whereby the spray guns impart a positive charge to the paint particles which are then attracted to the (negative) metal fuselage. As a result spraying losses have fallen from around 35% to only 10%.
Boeing have experimented with applying a nylon material between the primer and top coats so that when repainting becomes necessary, a paint stripper such as benzyl alcohol can be used just to remove the top coat. The intermediate coat process has been used on some B747s and 777s. The 3M Corporation are also conducting trials with a 'paintless' film system, but Boeing concluded that film is not a viable option for commercial aircraft for technical and economic reasons.
Behind every "no" is a "yes"