I always tell my customers to practice at home instead of learning this, like you say, 30 miles from home, in the rain.

I find it much easier to remove the rear tire if I have the bike upside down. It's a bad habit that I always do it this way, but it's easier than laying the bike down with the crank on the ground. Less balancing and I can use one hand on the rear derailleur and the other to lift the wheel out.