I also don't think a torque wrench is necessary unless you just want to go through an interesting engineering and manufacturing exercise. The knockoffs should always be tightened initially with the wheel off the ground to make sure the knockoff and wheel cones stay centered. The wire wheel and knockoff are designed to self-tighten as you drive (see "Rudge-Whitworth" at wikipedia), and I proved that to myself long ago by making "witness" marks on the knockoff and wheel hub. The marks ALWAYS move apart from each other in the tightening direction after driving a distance and I have never had a knockoff loosen in 33 years of Healeying.
A friend did report a problem to me with one of his knockoffs becoming loose frequently and he could always tell by the clicking sound from the wheel. I watched him tighten the knockoff and he was doing it with the wheel on the ground. When I told him to jack up the wheel and do it, he has not had the problem since.
My technique is to tighten the knockoff with the wheel off the ground by whacking it with the lead hammer buffered by a piece of wood. That avoids marring the knockoff as well as beating the hammer out of shape. I've been using the same lead hammer for 20 years or so now, although I have gone through a cord of wood. I whack until I don't see the knockoff move, then lower the wheel to the ground enough that it won't move when I whack the knockoff again a couple medium whacks (a "whack" is defined as proportional to the weight of the hammer times the speed of the head at impact, in case anyone asks). Then lower the wheel completely and Bob's your uncle.