My usual approach, for the majority of my armies has been to temporary base models, and more or less batch paint, but with each model receiving equal care and attention.
Inevitably, models will emerge as “better”, just because I posed them in a more attractive way, or because for whatever reason a steadier hand on those particular ones has made them come out better. So those guys go in the front ranks.
Where it’s monstrous infantry or large infantry, and it’s at regiment size, and there’s sufficient clearance between models, I’ve been putting them on their base (semi finished) and painting them there. Basically, cutting out individual temporary bases.
With troops, regiments and hordes of infantry and cav, they get more crowded on the base, if you’re at or near PMC, so I’ve tended in the past to use temporary basing for each model, even though this can mean - at times - making a lot of temporary bases out of whatever crap I have lying around.
Lately, however, for skeletons as pictured below, and Victrix knights (abyssal horsemen) I’ve been priming, putting them down on semi-finished bases, and just firing away with slapchop for the horsemen. The skeletons I painted with my kids and just used a super simple prime and speedpaints on top approach.
Will I attempt this with other ranked units in the future? I might. It was a timesaver, and for me “good enough” is done, we’re more about getting the models on the table to play than really enjoying the painting over a protracted period.
If you take the example of the abyssal horsemen here, one advantage of this approach when you’re using the slapchop method is that things primed in black can just be left “in shadow”, if they’re a part of the model that is unreachable, and thus likely to be largely unseen anyway.
The abyssal horsemen bases here still aren’t totally finished, I’ll do more to break up the puddle bases, which are still visible.