I just play with hair&fur tool in max in edit mode by hand, brush it etc. then make a copy and randomize it for more realism. then convertet in corona proxy cause it generated some bilions polys and slow down the viewport. Then I aply it a corona material with a fallof map in diffuse chanel with a dark and a bright color to create that specular effect u see on the top strands. But dont forget to put in on a plane with chamfered edges for base rug. I see a lot of rug test on guys but they forget to put a base mesh on to it, and they look like grow from the floor wich is wrong. Thats it! Its a more trial and erorr process.
And do that on a empty scene, save it some where as a proxy, then load it on ever scene u want. And a litlle tips, do the material test in a emty scene set it as a studio, and twick it until u get the desired effect. Its more easy to test render it, than do it in a real scene where u have a lot of other objects that generate more polys. The pain of hair&furr is because u dont understand how it works all that controlls, but once u get it, its just a fun game.
Here is a image of a scene I used this rug.
Hope u like it. :)