I've been using this technique for years and highly recommend it. I've only had to re-season my main pan from scratch once in five years, after accidently forgetting about it on the back porch for a week (that's Florida humidity for you).

It's great. I've seen people warn you to not wash your cast iron with soap so as to not damage the seasoning, but I use soap without fear. I've heard from others they even put their cast iron in the dish washer, although I haven't tried that personally. This creates a base layer of seasoning that's REALLY hard to get off.

Maybe it sounds like a lot of work, but it really isn't as long as you're not in a rush to get it all done in one day. I'd add a layer of oil, run the oven while I gave the kids their bath, and turned it off after. Maybe 5 minutes of work per day over 3-4 days.