For greatest realism, when painting a model railway locomotive should I have a matt, satin or gloss finish?

The ideal type of finish chosen by a modeller for painting a model railway locomotive will largely depend on personal preference and the level of realism the modeller is aiming to achieve. However, here's a general overview of the different types of finishes:

Matt Finish: A matt finish provides a flat, non-reflective surface, which can be useful for replicating the appearance of a weathered or older locomotive.

Satin Finish: A satin finish provides a low level of shine, which can help to replicate the appearance of a well-maintained locomotive. This finish is often used for modern locomotives and is a good compromise between a matt and gloss finish.

Gloss Finish: A high gloss finish provides a bright and shiny surface, which can be useful for replicating the appearance of a freshly painted or highly polished locomotive.

Ultimately, the choice of finish will depend on the desired look of the model and the conditions it is meant to represent. Some model railway enthusiasts prefer a more realistic look, while others prefer a more stylized or fantasy appearance. Some model railways may be run outdoors, which can affect the finish, so it is important to consider the conditions in which the model will be displayed and run.