-
For brass nipples i use rock n roll nipple cream because its not messy. Oil works well enough but there is cleaning to do afterwards. Each wheel builder has there own thing.
For alloy nipples to stop corrosion i use permabond threadlock.
Washers gets used on many build. Some rims they don't work with but of you can use them they reduce friction and speed up the build. If you build alot of wheels speed is of the essence.
I'm curious as to what prep you are using; any reason to avoid boiled linseed oil?