Incase you guys haven't noticed, the Shipbucket style in regard of shading has moved constantly towards getting rid of the darker grey lines. (I for example have completely dropped using them). The idea of showing the angles with different shade has also been around quite lot, but taken that Colo has been not here active for quite time and other critics haven't really drawn anything, I can understand if you feel sort of "drop" out from the progress
Bombhead and Hood with their RN ships have been the biggest pioneers of this techinque, and I myself have never forged my style on stone, when the world around be moves ahead. So does Shipbucket.
What comes to actuall use of this style of shading, I try to always use only two or three colors... ligther shade to express when things are turning inwards from the observers wiev, and darker when they are strecthing onwards (like it is in case with gun turrets tops). In case of the surface angling into two different directions, I use dark and ligth quite freely as the two colors doesen't really give away the direction of the angle, unless used with angle-flat-angle arragment with the normal shade being the flat, and each directions of the angled surfaced being the ligther and darker shade . In these turrets there isen't one, but flat-angle-another angle type of set. If I would use ligther shade on the reversed turrets (rear or front), then I couldn't use the ligther shade in expressing the inward angle of the top part.
Also, Im not stating this is the only way you can handle the angles... more that its just one way, when regarding the actual idea of shipbuckets two shade of same color...