One thing that I would add is to completely read the instructions and try to identify all the parts before starting.
I leave the small parts together as they are easier to identify that way and I also find that I do not lose them, which sometimes happens when they are loose and off the flashing.
I have never washed any parts of a resin kit. After building, I do prime all of my models with a flat black primer paint before final painting. After building over 60 resin kits that have been operating on my layout, I see no evidence of paint/surface failures.
I suggest that you drill and tap both for the trucks and couplers.
