How do I get brushes to rotate in a circle around a central point?
Make your brush, then make another brush touching it along where you want it to rotate. cover the second brush in the system->origin texture. Selece them both, right click on the selection and make it a func_rotating. It will now by default rotate around the origin covered brush, and about the Z-axis. You can change different properties of it by bringing up the entity window. (press n)
go to google.com type "rich diesal tutorial" hit enter and go to the first link. dont ask this sort of questions
...or he could just do what I said. But, yeah, that is a good tutorial. It still works for GTKRadiant, even though its made for JK2Radiant. This is the website for the richDiesal tutorials: http://richdiesal.jedioutcastmaps.com/tutorials/