Polishing the exterior of the intake manifold is a very labor-intensive project. You will have to be very patient if you want to get the best results and finish. I would advise you get a flex attachment for your Dremel tool and a variety of sanding bits. Don't worry about the finer shit for now. Just get a bunch of coarse grinder/sander bits and work the thing from end to end. I've also seen people have good results taking the larger surface areas to a wire wheel on a bench grinder. It's all in the steps and attention to detail.

As for the performance porting, if you're really new to this, I would highly suggest sending your spare TB and manifold to either Exile Racing or Eddy Fierro for professional porting. There is a bit of art to it, and the power comes from improving flow. This is a combination of volume and velocity. You just hog it out in there, you will lose power. Besides, polishing the outside will keep you busy enough! Let the pros do the subtle, internal port work to save you some time.