Are there any good tutorials (free or pay) for make high quality grunge maps?

I have painted a few but they are to low quality for close up renders.

Whats a grunge map?

A grunge map is grey scale image you would use as a transparency to apply a different level of texture too.

For example you would use a trans map to add dirt to an object or rust, tarnish ect..

I have filters that I can do this with but would like to learn how to paint them better by hand, it gives you more control on the overall appearance of how your final render looks. It really adds depth.

http://forums.cgsociety.org/showthread.php?t=373024
This is by Stonemason, it may be of some use to you.

Thanks. The sort of thing ,in Carrara, where you use the Anything Goos and Enhace C plugins from DigitalCarversGuild.

You want to make a brush stroke (by hand or using fractals) of some kind that you can stamp along the edges of your objects.  Or let procedural shading do it for you in Carrara.  Plugins like Anything Goos use edge detection so it's pretty much automatic when you hit the render button.

TerraMatrix - That’s just what I was looking for, thank you

I have Anything Goo's and Enhance C and they are great plug-ins but I thought it was time to learn the process as I will be testing my objects in a few different software environments.

Thanks for all the help everybody.