With the same Gillette Slim Adjustable razor and the same setting, 4, but a new platinum-and-PTFE-coated Dorco ST-301 blade, today I got the same close shave, but with less irritation. So clearly the blade makes a difference.
And yes, I did about the same three-pass shave, using largely oblique strokes.
Yet today's shave wasn't up to par. Still harsh to a degree -- close, but a bit harsh.
So once again, the answer is that though shaving technique matters, blade grind and coatings can also matter for those of us with rather sensitive skin. Also, razor design matters. Although the Gillette adjustable can have the blade gap varied according to preference, the blade angle is fixed by the design of the razor head. As I've said before, I believe that most TTO razors have an inherent characteristic of a relatively large blade angle, which is literally inclined to scrape a little more and cut a little less than razors with a shallower blade angle.
So tomorrow I complete the trial by putting the once-used Dorco blade into my Merkur 37C slant razor and having a go with that, confirming (I predict) that the harshness will be further reduced using this UTO razor.
By the way, my shaving ritual includes care for my shaving tools: the razor and blade. After every shave, in addition to rinsing and drying my razor (and, periodically, I lubricate them as well with either mineral oil for TTOs or petroleum jelly for three-piece razors), I dry and palm strop the blades. I think the palm stropping minimizes any potential micro oxidation and may slightly improve the sharpness on the finest part of the razor edge that must become exposed and degraded, despite any blade coatings, during the shaving process.
So as of today, at least, my recommendation to new DE shavers is unchanged: get a Merkur 33C, 34C, or a less-expensive facsimile such as the Lord LP1822L, and a good-but-not-expensive blade such as the Dorco ST-301, and shave for weeks and months with just that gear, perfecting your shaving ability. Then and only then, think about toying with gear to further tune your shave.
DE - double edge
PTFE - polytetrafluoroethylene; better known by its original brand name: Teflon
TTO - twist to open, or turn to open
UTO - unscrew to open (and disassemble); this design is implicit whenever one indicates a two- or three-piece DE razor.