That is interesting. Bart recommends regular bicubic, not bicubic sharper.
That's correct, even though the specific answer mentioned above was in relation to upsampling, deconvolution sharpening, and down-sampling again to the original size. Down-sampling image detail that exceeds the highest spatial frequencies of the smaller size will lead to aliasing artifacts, and the various resampling filters produce different artifacts as a result. Bi-cubic sharper produces horrible aliasing, even regular bicubic down-sampling improves with a prior blurring of the highest spatial frequencies. In the specific up/down-sampling suggestion, there will be little image detail to cause trouble (even with bicubic) because there is not much aliasing potential.
He also recommends Topaz detail for sharpening. I recently acquired the program on Bart's recommendation, but have not yet mastered its learning curve.
With the 'Detail' plugin it's important to grasp the difference between the regular Detail
and the Boost
sliders for all detail sizes. The Boost sliders target the low contrast detail (but with a correlation to the Detail strength setting), the regular sliders target higher contrast detail of the specific size one is modifying (enhancing or reducing). Since micro-detail is by definition of lower contrast, because it has a lower MTF, the Boost slider can compensate for that a bit as well. One has to avoid smooth surfaces such as defocused areas or sky, and Detail 3 has masking capabilities to achieve that if one is working out of e.g. Lightroom without layer functionality like in Photoshop.
As for Output sharpening use, this video
offers a reasonably good workflow explanation (using the older version of Detail, the newer version offers more tools such as masking thus reducing the need for Photoshop), although I'd also pay more attention to the "Deblur" panel, because it can mitigate some of the up-sampling blur. Good up-sampling generally should try to avoid adding big halos, and therefore produces low detail contrast which can be compensated for by deconvolution. This video
(again of the older, more limited version) does a good job of explaining the basic controls. Some of those controls are using an innovative approach towards changing luminosity (contrast), also the luminosity component of (complementary) colors.
Detail 3 also allows to specifically address shadows and/or highlights with different settings from the overall settings. It's important to note that the "Overall", "Shadow", and "Highlight" selections allow individual settings that will be combined! Shadows are usually dark because they receive less light, and that light is usually more diffuse/ambient than directional. If we have important detail in the shadows, but we do want to keep them dark, then we can use the shadow set of detail controls and regain some more detail there. That looks much more natural than adding too much fill light to accentuate subject structure in the shadows. Likewise, we may want to specifically target light sky structures with the highlight set of controls.
Does anyone know what downsizing algorithm would be used in LR?
I'm not sure, but it's quite decent. It's certainly better than regular Bi-cubic, and it produces much less aliasing than most filters/algorithms.