Yeah, I've tried doing that too, but GUI feedback is still very, very slow, it takes like 15-20 seconds to TAB to another filed with this mesh :(.
So that's why i hoped i could "tune in settings on just one piece" and then "live" all other layers and hit export, but it always meshes firs tin GUI = 5 minutes wait for it to finish, and then it saves file (Exported OBJ was 12 GB ).

Thanks anyway.