Here is a few shots of my production line. I like to try and build wagons in batches of five or more, it makes it a bit quicker build for me and easier to paint ten or more wagon at a time, less paint loss and airbrush cleaning.
After construction weight is added and held in with wood glue. I use this as it is cheap, it dosn't distort the models like some cheap superglues can and if you make a mistake or dribble it, it is easily removed when dry.
I don't really follow the NMRA standards with the weight, I just use what I consider to be a good weight.
After the glue dries the lids go on.