Paul
You will soon develop a feeling for how tight the nuts need to be. It doesn't have to be desperately tight because as Reg states they are self-tightening.
Regarding grease, I would just use a "standard" low melting point option rather than a copper based alternative on the spinner threads.
A Morgan-owning lubrication expert who no longer frequents this forum thought that the copper based greases could possibly reduce the coefficient of friction sufficiently to allow the wheel spinner to come undone in marginal situations . Although I have never heard of this happening , I respect his knowledge in these matters and have stuck to the cheaper alternatives ever since.
The copper based greases are fine for the splines , but the idea of using two different greases on adjacent areas just does not make much sense to me
, as I tended to do both jobs at the same time.
IIRC, I thought he advised against Moly (Molybdenum Disulfide) grease and coppa slip was okay, I've used copper based for many years & had no issues & also use it on wheel nuts for alloys
