Pre-Painting

Either/ both. How's that for a helpful answer.

Pre-painting creates a barrier for solvent glues, so assembly involves either scraping the paint away from the mating surfaces or using CA (super glue).

Painting after assembly covers any seam filling or other work done to hide assembly joints.

Armor modelers seem to "mostly" paint after assembly. Ship modelers tend to paint sub assemblies and then construct the final model.

For Aircraft what would you recommend?

For me, as with most people, its a bit of both. It largley depends on the colour of the parts. But things like undercarrage i will paint before fitting.

I tend to paint and assemble the cockpit, then assemble the fuselage, wings and tail.  Then mask off the cockpit and paint the whole thing.  Paint the canopy frames either on or off after checking the fit.  Landing gear can be done as a last step since they tend to have a few colors and details to bring out and glue in with either CA or 5 min. epoxy.

Some canopies have A/M masks available that make that nasty (for me) job a breeze, but there are ways to make it easier in a couple of steps.

LoneWolf13

For Aircraft what would you recommend?

 

There is no set rule/suggestion whether you paint first or not. It all depends on the part/piece/sub-assembly. You have to figure out what works best for yourself. Obviously, you can’t paint the entire unpainted cockpit once the fuselage is buttoned up. Don’t sweat it. You’ll figure it out. 

Further to that...

The biggest mistake I think modelers new or returning make; is to be on some sort of time schedule.

When I was young, we'd slap together a kit in an afternoon. Sometimes those habits are hard to break.

Just take your time and learn as you go.