Starting with, what we shall call, the carriages, there are some large mould runners on the underside of all the resin parts.
I trimmed these off with some flush-cut wire cutters. The resin is soft and they chew through it perfectly. Any leftovers were sliced away with a sharp knife and then sanded with an abrasive stick.
To be honest, it's all underneath so perfection isn't required.
The bogies are solid whitemetal castings. When looking to build a working model, I did find some Graham Farish wagons with the right sort of size bogies but these were on pricey modern PW hoppers (I think, it was while ago) although the container wagons could also have donated sets.
Assembly simply requires some superglue on the bogie and the wagon placed on top of this. The lumps sticking out from the centre well on the wagon are (I think) supposed to locate in to depressions in the end of each bogie but I felt they pushed them too close to the ends so lopped these off too.
Not owning an N gauge straight track, I Blu-tacked some flexi down between a couple of rulers and then set the carriage up on this to ensure the wheels were all in a line. I suppose a couple of screws or bolts could have worked as pivots but it didn't seem worth the effort for solid bogies.