Assuming you want lowpoly objects you would do it with lowpolygeometry, otherwise normal maps, If you want a more detailed version you would do it with displacement/Tesselation. There is nothing special to it, you will have to model the objects individually or apply decals, or procedural ones with substance for example. Depends really on what type of damage you want to do.
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Yeah I saw it in the last updates of UE4 but not tried yet.