I’m not sure what program you use, but copying and moving an unwrap to a new channel in 3ds max takes about 5 seconds. If you do a great unwrap on it and then let UE4 do the lightmap, it’s really not bad. I did it for every asset in my last build and it came out great. Even with more organic models.
There isn’t a secret channel for reflections. Reflections are built in the reflection map I think? Basically it’s stored in the reflection sphere or reflection box, whichever you’re using.