??? Where do you start ???

I used to do that as a kid. I found it to be much cleaner painting after the kit is assembled, or in some cases, sub-assembled. That way there's no touch up of glue marks. I used to do that method with indie tracks, but have since discovered an easier way of doing them.

I primarily build planes, I build them, then paint them. Only when I work with a very good fitting kit (Tamiya quality)  I might leave the kit in sub assemblies during painting and then assemble.

I'm a plane guy as well & generally paint sub assemblies like cockpit, bomb bays, gear bays & landing gear before fitting them. I then mask these areas when painting the fuselage / wings / exterior - this allows ill-fitting seams & what not to be filled / repaired before painting. I usually fix things like landing gear, landing gear doors & probes after final paint.

Usually my painting is done in sub-assemblies, or in some cases, sub-sub-assemblies.

I go by how the kit is but usually assemble a little, paint a little, and so on. You need to do what you are most comfortable with and nothing else.

Every kit is different. It depends a lot on the prototype- which seams are visible and which are not.  Seams that are visible can, with careful fitting, go together well enough they do not need to be filled and repainted.  The first step in any build is planning.  What do I paint as a seperate part, which do I paint as assemblies, and what do I paint as a completed (or almost completed) model? I virtually always put landing gear on after assembly and painting of the main assembly unless that is absolutely impossible.  In that case gear is painted as part, and masked after installation.  I have yet to find a plane that has to have wheels put on before last step.

Ships really require planning, as superstructures are generally different color than decks, and deck is hard to mask after supestructure is added, so I think ships have most variation in the plan of attack.

By "Number Cards" I think you mean "Parts Trees" or "Sprues".. They're also known as "Runners", although one doesn't hear that term often..

If you can't see ALL of the part AND get a brush to it easily after it's assembled, paint it before you assemble it... And you don't need to prime anything but metal, with the exception of metallic finishes... Sometimes you don't have to do that, as when you're finishing an aircraft that's actually painted with aluminum paint..

Working in sub-assemblies is always the best approach with tanks and other AFVs, and with most aircraft...

I don't paint parts "on the sprue" except for parts that can get a quick shot of spray Zinc Chromate primers, or aluminum, or RLM grey (whatever's called for) for the base-color.  For instance, when doing aircraft, I like to to shoot the interiors of the fuselage, gear-bays, bomb-bays,  and cockpit floors and bulkheads in one step...

As for doing washes, I generally do those after the parts are in the sub-assembly, but don't stop there.. You need to combines washes with dry-brushing... Washes add depth to details, dry-brushing is for high-lighting them.. Use the two techniques together on interior parts.... Base-color, then detail-painting, then wash, then drybrush...

Painting some parts on the trees is ok though, especially if they're small and a different color than the part they get attached to...  I generally cut the part from the tree, leaving a bit of sprue on either side of the part for a handle... There's no law that says you have to keep your sprues in one piece, lol.. But, if you do, make sure you either leave the number tag on the sprue section you cut out, or write it on the part or sprue with a Sharpie or something similar, if there are "Left and Right" versions of the same parts... You WILL forget...

One major exception to removing parts and then painting them?  Tank and AFV roadwheels... I leave those on the sprues and shoot 'em with the base color befre I even start assembly.. I'll touch them up with a brush later, when I sand the mold seams and paint the rubber portions...

"If you can't see ALL of the part AND get a brush to it easily after it's assembled, paint it before you assemble it.."

Says it all right there basically. If I can build the entire model and then get to all of it AFTER it is assembled, then there is no reason to not do it this way as gluing parts to a partially painted model is as much a hell as trying to paint a mostly assembled model.

But an airbrush makes all the difference too. Atomized paint spray is incredibly good at getting into areas you might think nearly impossible to brush paint.

Painting after assembly is nice for a lot of aspects of the construction, but it always depends on the subject. Interior locations simply have to be done first.

OP- you realize of course that if you paint the parts first, you can't use solvent glue. For me it's a combo and totally depends on the kit. Tanks yeah- stick a skewer up the barrel and shoot the whole thing.

Ships- lot's of pre painting. Typically parts have more than one color, and a lot of masking gets to be a PITA.

Airplanes- has to mostly be after because of the filler and sanding. Bottom first, then top.

only chuck norris can finish to glue a whole model, sand it with fingers and performing a flying kick can perfectly paint the cockpit\ inside parts after

too late time to sleep