Frankly, in my opinion, the only way to learn how to port is trial and error. Lots of error. It's always been suggested that the first part you ever try to port should NOT be one that you need. Most old hot-rod guys I know would go get some junk heads/manifolds from a yard and practice on them, just to avoid F*ing up something they need to use. It's always surprising how fast metal comes off a part when you shove a spinning carbide bit into it!
My emoticon is this
...it's my favorite!