While testing our 2015 Christmas layout project, we have run our two scale Berkshires heavily. I have to share with you that Mega-Steam's Christmas Berry scent is one of the very best I have EVER used. It has a very pleasant aroma and fills the room with a good feeling. I like it so much that I will use it regularly in our main layout as well.
If you haven't tried it, I would get my hands on this scent and put it in one of your engines.