I have polished one rocker cover myself so far, took hours though but looks like a mirror. Also i have polished up all the bits on the front of the motor that are visable with the covers on and have just about finished the bit that is just behind the plastic thermostat housing. Getting the intake manifold polished prefessionally for about $230.
Basically u have to remove all the casting marks, i have been using an electric sander to do this. Start at p80 and work ur way to p800 or so. Then using a metal polish start polishing! U know u have finished when u have lost feeling in ur arms and ur fingers are all cut up and stinging.