We cover paint techniques in the article within the Exterior Protection
What we will say here is that if you are undertaking the painting yourself then there are a couple of factors to consider.
If you have the use of a boat shed, covered dock, poly-tunnel or such like then your options are greatly increased.
If you are painting in winter in a cold shed then expect extended drying times on paint. Professionals will be practised in the use of additives for increasing or decreasing the pot-life, or curing time, on their chosen paint systems. Cold spots even in heated boat sheds can make final finish painting in the depths of winter a challenging prospect. A soft paint surface can cause subsequent applications to drag and spoil the final finish. If you are undertaking a self-fit then leaving paint to the professionals may be a sensible option in the long run.
Maybe consider laying down a basic enamel coat over the primer coats your shell will be delivered in to seal the primer. Primer is rough and porous and will very quickly allow moisture through to the steel below causing more issues than it prevents. A quick application of a protective coat in the colour of your final choice can be sanded back when the time comes to lay the paint down properly.