This is what I did with a tiny ball shaped carbide bur bit. It was horribly slow and way too small for taking out as much metal as I needed to.:
Then I got this sweet set of bits from a friend of mine to borrow. Needless to say, having the right tools makes a world of difference.
I hogged out this 1/2 of the port in 2 minutes to show you guys some progress. I took it down to about 95% so all I have to do is polish/finish the ports smooth. I would grind for about 30 sec, dip it in motorcycle gear/motor oil, let some drip onto the area I was porting and grind away.
This is super easy. Get some good lighting and take your time sweeping the bit so you don't dig in. Any damage you think you might have done most likely can be fixed. If it starts to jump around on you hold onto the die grinder a little tighter and don't push so hard
2 minutes of grinding with this one bit:
You can see the tiny bit I started porting with laying in the case:
P.S. Bugzuki, I love you for making these plates. I would say these are a must for beginner porters....