Having painted the upperworks in your choice of basic grey, I would I would tack the superstructure parts which are going to need to be camouflaged together, and then mark out the camouflage pattern with a soft, but sharp, pencil. You could almost certainly do this freehand, armed with a good set of camo profiles, such as those provided here:
http://www.bismarck-class.dk/bismarck/paint_schemes/paintbism1941.html
http://www.bismarck-class.dk/bismarck/paint_schemes/paintbism1941rheinubung.html
Notice how, at the beginning of operation Rheinubung, the upperworks camo stripes had been overpainted. If you were to model the ship at this stage of her career, this makes things considerably simpler.
I would then disassemble the model into its sub-assemblies, mask and spray. This approach is suggested by Tamiya in their 1/350 Prince of Wales, which, as you know, has a complex, straight-edged, camouflage scheme.
You might prefer to spray the camo striping first, after priming but before the basic grey. It would involve less, and easier, masking. I often adopt this approach with things like anti-dazzle panels on aircraft, and boot-toipping on ships.
I would do this before adding any detail parts or etch. Where etched parts needed to be camouflaged, I would paint these freehand. This is the approach I intend to take with the Revell Germany kit, even though the kit provdes decals for the hull camouflage. I intend to use these decals to make templates.
An alternative approach might be to use decal striping - aftermarket black and white striping of appropriate width is easily available. Again, you would need to measure out the width of the stripes, and I imagine you would need large amounts of decal solvent, especially on parts like the funnels.
HTH,
Cheers,
Chris.
Cute and cuddly, boys, cute and cuddly!