I've actually had mantracker training and I think trying to leave no sign is a waste of time. You'd be better of using that time to move at a normal pace to cover as much ground as possible without being obvious.

There are things you can do to make your sign hard to read. Contamination is the worst IMO. Walk where a lot of other people have (or will in the near future...better yet) and your tracks will be obscured by those of others. This can really slow a tracker down as they need to make sure they're following you. The size of print you leave will be an indicator which could seperate your tracks from others in the same area. There are very slick techniques for accurately measuring foot and pace size on the run without having to stop for very long.

The other thing you can do...and it's hard to do because it's not exactly practical...is wear shoes which won't leave a 'signature' print. If the tracker can't identify the tread pattern of your footware he won't have any obvious way to seperate you from other tracks he may find...this can really slow them down (I know it does me). There is a possibility he'll follow the wrong ones too. Trust me...this is way harder than it sounds...I've tried just to see and usually I leave MORE sign. Going barefoot doesn't help because then you're leaving the equivalent of finger prints behind. Wearing footwear like a moccasin can help but isn't fool proof.

Changing your pace and occationally 'hoping' around can mix somebody up too especially if there is a lot of contamination. They'll find you either way but it might slow them down if they can't find your exit path right away.

Also, avoid 'track traps' like muddy patches or sandy soil or water/puddles...stuff that really makes it clear what kind of shoes you have on and can tell the tracker a lot about you.

Most of the mistakes I have made tracking have come from following the wrong set of tracks because I couldn't seperate 2 (or more) sets and just simply picked the wrong ones to follow. That's when you get into behavioral profiling and trying to use other techniques to ID your tracks...like trying to figure out if the tracks are from a male or female, a limp or not, or if the person is tired, how much they weigh. That's advanced stuff which I've only touched the tip of at best.

In the example you provided above (getting on topic again) I'd walk around the fence parallel to it. I wouldn't be 'careful' or run (that will show in your tracks and could give you up). I'd imagine on a farm there's more traffic there than anywhere else. Maybe more on the inside than the outside if lifestock are a factor (they can cover your tracks with their own too). Cutting through a field that has no tracks to speak of will give you away almost as easily as a cut fence or gate chain (though those things will give them a definitive last known position to start cutting from). An experienced sign cutter will pick your path out in seconds and won't need to spend time analysing it...they'll follow it like there's a big red arrow painted on the ground. If you're going to be going through farm country wear the same kind of footwear the farmers do even if that means cowboy boots. If all the tracks are flat leather soles with a square heel, they'll have to slow down to distinguish them to find yours...or better yet won't know which ones are yours in the first place.

It's a pretty scary thing. I didn't realize just how fool proof it is until I started learning it myself.