Cast Iron Skillet Care

I love my cast iron skillets. I have 4, two 8", a 9" and a 12" That's it... I use the small one for a single burger, and it always burns on the bottom from the crusty burger and burnt on cheese and fat.
Here's how I clean it:  I let it cool off a little and fill it with water with NO dish soap and let it soak 10 minutes, and ONLY 10 minutes, or else it will rust! So I put the timer on. When I return I scrape out the bottom of the skillet with a metal spatula and then with a "Golden Fleece" pot scrubber. Then I dry it out and place it on a burner on the stove and turn it on for a minute or two. When it cools down some I spray the inside of the skillet with oil spray. I prefer Olive Oil Spray.