Guys, I just reached 2000 models in max and about lightmaps, the only thing I do is change channel to 2 and click Abandon. However, I found this script SteamRoller, so I wonder will it help me automatically to flatten all the UVs for lightmaps?
Gosh, I would kill myself if I have to unwrap all 2000 models manually again 
Silly question - but doesn’t UE4 have automatic lightmap unwrapping, or does that produce poor results?
Oh, sorry. I just changed lightmap resolution to 256 and everything is great. Nevermind the question, thanks!
UE4 has a lightmap generator that uses the UVs from channel 0. It doesn’t generate, but lays out existing uvs and spaces them sufficiently. The quality of the UE4 generated lightmaps depend on how well channel 0 is laid out. Honestly though it’s pretty easy to do in your modeling package.