... -_- that's because you're no mapper. In the most obvious case, he's talking about he hl engine. Anyway, if you want moving trees, i'd suggest you get some models or have someone model then for you, and with an idle animation that resembles that of a tree standing in the wind. As for cars, and such, i think you'd have to use the func_train and set a path. I'm no entity expert, but that's how i think it's done. If someone cares to elaborate this some further, be my guest.
That's just about it for making trains, as far as I remember. Use path_track and path_corner entities to lay out your path. If you want the train to be controllable, make it a func_tracktrain and provide a func_traincontrols entity. (If they're in the .fgd; I can't remember and I'm not able to check at the moment)
Models can be animated so it looks like they are moving in the wind. it's impposible to do that as smooth with brushes in hl engine =/
Niobe, you seem to post things that, well, a lot of times do not agree with the laws of mapping. Do a little more research, before you post such things. I'm not flaming you, but i'm giving you ordinary advice.
a good engine doen't nead animations in the model to move, it neads to be able to move in the map.
and as smooth as brushes is possable, you just nead to know how.(btw, there is no wint in the game and ther is also no entity for that so wy even put a model with that animation in it)