Ah I see. Guess I got mixed up XD.Pretty sure you won't be able to find Porygon as shiny yet. I meant Beldum as the shiny. What I meant is because Beldum's shiny is already out from the Community Day, it can be obtained shiny but at a much lower rate.
But still I found a wild Charizard and I caught it! It took a while for me to catch it since it was dodging a lot of balls and it kept on escaping. That was my first wild encounter with a Charizard.
Sweet find! Last wild starter I found was a Blastoise and it ran away.