Every guide I can find on the internet tells me to heat it up till the oil is smoking in the pan, but none tells me exactly how long. What is the criteria for knowing that the amount of polymerization is sufficient? 
The best way to season cast iron or steel pans is simply to use them.  The more you use them, the better they get.  Just don't use acidic ingredients, or clean with soap and water.  Scrape them out when necessary and wipe out.  Once clean, apply a light layer of oil with a cloth.  That's it.  If heavier cleaning is necessary, put a layer of coarse salt in the pan.  Heat and scrape with a wood spatula. Wipe out, and proceed with light layer of oil.  Most people over complicate this. You may deal with a less than perfect pan the first couple of times, but this will soon pass as long as you care for your pan as I've described. 