Quoted from Spyderturbo007:
I do mine differently than how I've read most people do it. I add the oil and seasoning at the same time to a cold kettle. Once the oil is melted, I add the corn. After that, it takes about 5-6 minutes for it to pop. I also dump it pretty early as well, when it's in the neighborhood of 1 - 2 pops / second.
After doing about 100 batches, I find this tastes the best to me. I've tried it the way some people suggest and wait for the oil to get hot, but I don't think it tastes as good as when you add it initially. You'll also notice that if you do it that way, the popcorn looks more white.
It's going to be slightly spongy right after popping because of all the steam. It's the best if you pop it ahead of time and let it sit in the kettle with the warming tray turned on for about an hour or so.
+1 on this...
I have an 8oz Gold Medal. I put the oil seasoning pack in first and then let it melt (It doesn't take long). Then in with the popcorn. I always pop with the front doors open to release the steam and get the smell flowing too. I think that might help with the your sponginess as well. Mine also has a heated tray at the bottom that helps keep it crispy like the theaters. If you want it stale like the circus popcorn and sporting events stuff they sell in those red/white boxes, just leave sit it in there for a day or two before eating it.
The popcorn never pops instantly, always takes a little bit even if the oil is hot... Happy popping!