Quoted from Parzival:

I love my popcorn machine, and got a lot of good recommendations from the earlier mentioned thread. Here is what I use, minimal upkeep, great popcorn everytime:
Machine - amazon.com link »
Popcorn/oil/salt - amazon.com link »
Extra seasoning - amazon.com link »
Butter type topping (really makes it taste like the theaters) - amazon.com link »
I sprinkle a bit of extra seasoning, then use a squirt bottle for the butterish liquid

Quoted from Jman44:

I have a small 4oz movie theater style popper, works good but it has never produced movie theater quality popcorn... until today. I have always wondered why theater popcorn has that perfect cruchiness to it but I couldn't replicate it at home.
Many will say it is about the oil temperature not being hot enough but that is only a very small part of the problem. Theaters actually have "popcorn conditioners"(the display case) that they put their popcorn in. It blows hot air over the popcorn to keep it warm but more importantly to crisp it up perfectly crunchy.
I don't have a "popcorn conditioner" nor do I really want to buy one, but I do have a common alternative though. An air fryer. I put my freshly popped popcorn or even day old popcorn in the air fryer for a few minutes and it gives it that perfect crunch I was desiring.