real rust

hi guys, readin the several forums over and over i didn't read anything about making real rust to put on your models , here's a tip i used for several years now : take a (do not know what it calls) full 'sort of metal' sponge( the sort that can be used for cleaning stoves) dip it in some water to make it wet , squeez the excess water out and lay it in a tray outside in all weather. After time (can take some weeks) the sponge is falling apart and what is left over is real powder rust. I think it depends on what humidity the weather is that have a effect on the colour of rust ( have made rust in the winter and summer and they have a different colour , from almoust black to light brown). To put it on your armour , make a past with the rust and matt varnish and aply it where you like it ( it works great and it's real ), hope this whill help. greating from belgium