Druchii.net

I was thinking of buying an used but unpainted dark elf army. I was wondering how hard they were to paint when already assembled compared to painting the pieces and the assembling them? Would you typically want to paint at least some parts prior to assembling?

For me, it would very much depend on the models. If they have cloaks and such or weapons going directly in front of their chests, those parts would probably be painted separately. On the other hand, if all parts of the model can be reached, it's easier and more comfortable for me to assemble it first, superglue can be messy after all.
If you look at my own models, for example, out of these only the spearelves were painted separately (cloak+torso+head, legs and arms), the others were assembled first or in one piece to begin with. The spearelves were very difficult to paint as whole models, though, luckily they were pretty easy to tear apart.

It really depends on the model and the painter. For tabletop standards, though, it should be fine to assemble first and paint later.

Personally I like to have room to paint, so I'll gladly leave a few parts unassembled if that makes it easier to paint the pieces properly. But then that is a very time consuming proces so I try to keep it only where necessary.
For example, the old 6th edition warriors with spears. They paint very easily if you assemble the legs, torso and heads first and paint that before adding weapons and arms. But I found I can still paint them quite easily if I glue the spear on the model as well (and it's easier to make the model rank). So, I only leave out the shield arm, and shield which I paint separately now.

Where possible I always assemble first so I can fill any gaps with greenstuff and file smooth, generally leave shields and any mounted models to be painted separately though

I always assemble first as well! - never done it the other way.

I think it depends on the model and your ability. Over the years I've found that I can manipulate my brush and control my paint better than I could when I just got started so I can build more of a model before I paint. Sometimes metal models give me grief because of the poses they are put but I can usually work through it with a few touch ups.