Use a rotary type grinder like the dremel. I like to use 'A'
to cut into aluminum the teeth don't load as much and it cuts a lot faster. Depending on how aggressive I get I can port match a case in as little as 15min with it.
For best results use a gasket to trace the ports onto the case. There is a slight issue with the metra 65 kits, the ports are a bit lopsided on the kits but not on the gaskets. I just ported my first 65 metra case a few weeks ago and I matched the gasket (aluminum one) to the kit and then the case to the gasket to the case.
As for the actual case grinding, it depends. From the feedback I have received from the cases I have done the more of the original material you leave the better your mid range will be. If you profile the ports all the way to the back of the case you will improve the flow but it will show up more on the top end.
Get comfortable with dremeling first I really like the extension, holding a something shaped like a pencil vs something shaped like a brick has a lot to do with what the final product will look like.
When you are ready to attack the case I like to hold the dremel so that I will make a 45 degree cut into the case. I go around the whole port window and open it up to within about 1-2mm of the final dimension. This will allow you to clean up the port without going oversized. After you go around the port at a 45 degree angle you will be left with a steep transition. I then go back and round over that sharp angle and smooth it into the original port shape.
After you are done smoothing the port go back and open it up to the final dimension.
Little sanding and your done.
Thanks for the props Elliot!
I need to film the next case I port...