It seems any cloth I start to weight paint becomes very slow… even moving brush over the mesh is at slideshow speed.
When I’ve watched several tutorials around Unreal weight painting, I see everyone similarly complex mesh just quickly weight paints and have never seen anyone on internet even coming across around slowness of weight painting in Unreal.
First I was using my cloth mesh created in Blender… Then I’ve tried also IClone sold in Content store imported cloth to test, if I had some wrong mesh topology with something profesionally created, but it was slow also.
Is there something I need to watch out? I understand that vertices count can be an issue, but those didn’t seem to have too much triangles. And also in Blender I can weight paint bones superquick as expected on the same mesh.
Slide-show speed effectively hinders to actually paint accurately … even moving brush cursor over mesh redraws with 2-3 seconds lag 
Actuall rendering physics of the same cloth is super smooth… but when clicking on Cloth weight paint button takes about minute to start painting, and weight painting itself is slow also, as I’ve mentioned, and UI regains speed reactivity after leaving cloth weight paint mode.
Or may be the problem when using IClone default HQ characters and those skeletal meshes have to be optimized for using cloth weight painting? Not sure why, but in Blender weight painting works fluently, so it seems there is some other problem. But I guess there is no way to import weight paints into Unreal from other software?