www.kraytracing.com

Most of the textures that needed dirt, like the concrete wall, the window frame, railing, back-wall panel, pool andconcrete, used the VrayBlendMaterial.usually with 1st and 2nd blend amount..

which is the best way to smilute this on kray?

Try this:
http://katastro.fi/~eetu/grit3/

Actually I have plans back to this with concrete surfaces....