Trading on the overpriced favourite
Here is the idea of this example:
Remember the favourite's price at the beginning of the race/match/event. If later its price has grown up by no less than 20%, back it. As soon as it hits the starting price of falls below, lay it to green up equally.
I've created two triggers: one for UK races, as they have starting prices, and another one for all other sports.
To change difference in price from 20% to something else, edit the first condition of the trigger named "backing the favourite". The number 1.2 corresponds with 20% price change, so if you need, say, 10%, input 1.1. For 15% it would be 1.15 and so on.
Here's an example of how the triggers will bet in UK races: