I agree with everything Colin says but would just add another comment.  With one kit I built, which included a large number of white metal fittings, I would always make a decision as regards whether it would be best to use the supplied white metal part, with all the associated cleaning up and concerns as regards lack of strength, or whether a scratch built part might actually be less work and look better.

As an example the kit included cast white metal ladders.  They were actually quite heavy and would have required a lot of work to dress them up to an acceptable standard.

I decided it would be easier to scratch build my own from stripwood.  This proved to be significantly less work and gave a better result.

Another example was a vertical ladder, which was broken so I had to make something from scratch anyway but the result was much better and far easier than dressing up.

I never use white metal handrail stanchions as they are so weak.  I always replace them with brass stanchions and brass rails between them for a much stronger and neater finish.

Next the life belts were also cast white metal and I decided that they would take a lot of work to clean up to a suitable standard.  Again less work and a better looking result was obtained by scratch building.

Finally I really didn’t like the oars supplied for the lifeboat and the dinghy as they were going to need a lot of cleaning up and they were so weak they bend out of shape very easily.  They were replaced with meat skewers and stripwood and the leather cuffs were made from brown heat shrink.

Just some things to consider when dealing with white metal fittings.