Like de_nuke, de_train doesn’t have many trick smokes you can throw. You can smoke off CT Mid from T spawn with this smoke:
Other than that, smoking upper and lower at B, and smoking both crow’s nests when retaking A are all viable uses. There are so many things to bounce smokes off, there is little point in running through a set position when there are 20 other variations that will get the same result. Anyway, if you have read through the other smoke grenade advice posts you should have some idea of why and when to use smokes – and that’s really more useful than knowing a handful of dedicated throws.