Hi Hornet,
Yes, there is a white grease that Pro wheel builders use during lacing.
There is a torque wrench available for setting the nipples up.
They are made in the States and don't cost all that much.
If you over tighten your nipples you will get a flat spot on the rim or your rim will not be centred on the hub.
When building a wheel the rim is centred on the hub and then the rim is trued. The next process is to torque up the nipples, this is done slowly by a quarter turn on each nipple all round the wheel on both sides. When you reach the beginning again if the nipples are still not torqued up you have to repeat until they are right. The oil or grease removes most of the friction so a true torque reading can be made.
Your mechanic sounds like a great guy for working your nipples gently and using lube.
As I said they strip out so easily, and I don't mean the thread I mean the four straight sides that you place the spanner on.
Ji