Boilerman posted a video of him removing side rails, so you can search for that.

The basic trick is to get the spiral nail head raised up enough to get a grip on it with something else. You need to get them started by flexing up the side rail underneath it with a putty knife. Once the nail head is pushed up a bit, then you can grab it with another tool. A tack puller is good, if it's flush and thin enough. I use a really old wire cutter that happens to have a flush side to it, so I can get under the nail head without much clearance.

Then the other trick is to twist the nail counterclockwise as you pull, and it will basically unscrew its way out. You can pull it straight out with a tack puller if there's enough clearance, but twisting it makes it work when you only have a little grab on it.

Cover any surfaces that could get scratched in the process.