Atomized bubbles while following Park process to bleed Magura MT5
I thought the sealed system would prevent oil from tumbling out the caliper-side port, similar to how I can use a straw and my finger to lift coke out of a glass. But it doesn't seem to be the case here

I had similar experience with Magura brakes — just shutting the lever-side port closed did not stop oil from leaking from the caliper body's opening.

One variation from the Park guide that I did my second time was detach the caliper from the fork and bring the vent hole up to parity with the lever-side vent so that I didn't leak oil or leave space when I put the stopper bolt on. That seems to have helped.

Raising the caliper body at the lever's level is what the official Magura video tells us to do; see timestamp 3:30.

And I guess secondly is there a followup process I could do to further purge any remaining air from the system?

When I had problems with banishing of remaining bubbles from my Magura calipers after a full bleed process, a follow-up quick bleeding process helped me. See the official video:

                
            
Because only the lever's port gets opened during this process, there are no dangers of introducing new air to the system via the bottom hole.
I used Magura's own bleeding kit with a syringe with a hole at 30 ml mark to achieve so. I do not know whether Park Tool's kit that you have has a matching device or not. If nothing else, you can make it yourself from a regular 30 ml syringe and a needle.
Good luck!