SharePoint PowerShell Library Folder permissions

Hi

I’m new to both SharePoint (2010) and PowerShell (and Microsoft in general. Linux was my thing. I’ve decided to come to the dark side for a while :)  ). Anyway, how do you set permissions for a specific user, for a specific folder, within another specific folder, for a specific library in SharePoint, using PowerShell?

For Example.

 “Meetings” (Library)

ÊIT Services (Folder)

ÊIncidents (sub Folder)

               ÊDecember2012 (sub Folder) Grant “Read Only” access to “Tim Smith”

(in other words, in the Library "Meetings", there is a folder "IT services", in that is a folder "Incidents", and in that folder is another folder called "December2012")

Yes, I can just do it manually from the GUI, but I will need to do this a number of times (different folders and different users). I can spit out a list of all the folders (and sub folders) for a library; I’m just not sure what commend to run, to assign the permission on that folder, for a given user.