When a Calibration Engineer/Metrologist/NIST-tracable, BTW (having to deal with the subject), we dealt exclusively with Mountz.
We tended towards in-oz, (had some in-lbs applications - theory still applies .... but their drives (manual or electric) were the only way to go - accuracy & repeatability. No others made the grade - sorry.
Oiling a torque driver & you better always have the exact same amount of lube, no out-gassing/no migration - nothing - or your applied torque changes. They're designed to work with no lube, BTW, for that very reason - lube changes = so does your torque value applied.
Likely, anything that'll repeat within a +/- 5 ft-lbs will do the trick enough for bedding screws though Art's hanging a 5 lb weight off a foot-long works just as well, as will just "getting the feel of it." Anything short of stripping the threads while having "decent enough" torque works plenty good.
& anybody thinking that "anything's forever" & you don't need to re-calibrate has no inkling of the matter.
Whatever - just make sure your bullets impact correctly afterwards, huh? ')l