I do some strictly amateur video editing, but have been using Sound Forge to separate out whistles, bells, steam sounds, pop offs, etc. By using several audio tracks, you can get very well synced sound! It is just a lot of work. This program lets you cut and paste sounds, and even change pitch without effecting time, or change time without changing pitch. This is great to get the whistle to blow in sync with the steam plume, or to speed up the exhaust to match the speed of the engine. The few minutes I've done, working with shots of a standard gauge shay (chugging is a lot easier to get right with one of these!) have come out much better than the generalized sound usually seen in videos! With a good sound library on hard disc, of the proper engine, it seems like the way to go.
Steve