i like building with plywood, however, when done and painted you can see the grain in the wood which doesn't look to good when the model is of a steel vessel. There are various ways to seal the grain so it doesn't show up. My favourite is to use car body icing to fill the grain. Its a two part mix that applies extremely smoothly, sands well, takes paint and looks great when done.
Mix the cream as per instruction. Working fast, apply it to the model in a thin layer. When it hardens, sand until smooth and apply a primer, then paint of your choice. the effect is of a metal surface with no grain showing through.
John