Those of you who do their own set ups?

 Mine are all dual action on my acoustics. The first one I adjusted was the Seagull and it was not loose it was just much easier to turn and smoother than the RK and Ibanez AC340. On all 3 I needed to remove some relief I always either have the strings off or slacken all when removing relief, not when adding it, as you said the strings help.

 Sure there is resistance because the rod is bending the neck. I just think it's possible that some companies don't bother with even a drop of oil on the threads before they install it in the neck. I imagine most companies don't make their own truss rods. Just like the tuning keys , frets , strap buttons. 

 I feel you be able to adjust a trust rod and have the adjustment smooth without having to apply more force than needed, I like to feel when the rod is acting not wonder why I need to push harder than needed.

 I could turn it without it feeling like it would snap , it didn't make any noises that would concern me. It didn't feel like it was trying to move back by itself like it was twisting like a torsion bar. It felt like the recording king and I adjusted that a few times , it did work and removed the relief I wanted. I would be more concerned with the weld that holds the adjustment part to the rod snapping off before the rod would. You can't see the weld. I feel the Seagull used a better quality rod or at least oiled the threads because it was far easier to turn and worked very well. I have this POS Epiphone AJ-100 and it has the adjustment at the peg head and it was not difficult to turn. I doubt any company other than perhaps the US made guitars are going to ever offer any info on where they buy the rods.  I know they all use the same 4mm  hex wrench and very well could be made by the same company for all the made in China or Indonesia acoustics. All the adjustment heads look the same. What I do think yet have no proof is they just don't lube the threads. I don't see the point of working a rod back and forth to see if it frees the threads up more , that seems counter productive as  well as the possibility of causing more issues than they have now. The electrics I built I made a few one way rods and bought 4 that are 1/4" dia rods in an aluminum channel and you can remove the nut so I lubed them. The dual action are now pretty much the norm these days on most brands which do offer the advantage of not depending on string pull to add relief, Sure some still use these they are just not as common any more.

 One thing I do recall way back in 63 I had this Kay thin line with double cutaways and didn't know how to get the action lower, I had the bridge screws down as far as they would go then went for the truss rod and it took quite a few turns before it snapped it was just a one way rod. and I probably ran out of threads , what did  I know . the neck angle was probably off. I was a bolt on neck just like Harmony Rockets were. I don't fool with truss rods unless the relief is too much I have only adjusted 3 of my acoustics. The other three have the relief set where it needs to be and have not changed I just leave well enough alone. The AC340 did come with a small book in all the languages and said to take it to a  pro, yet the plastic bag the adjustment wrench was in had instructions stating to loosen the 2 middle strings to adjust , never said the sane thing to slacken all the EL-00 had the same statement just so one could remove the cover. It was just common sense for me to slacken all the strings , why fight string tension.