Trocas are types of moves used to quickly switch feet. This particular troca is used to get in position for the entrance to meia lua de compasso.
Focus on bringing the front foot slightly back (probably just a few inches) first and then quickly switching with the back foot. Be careful not to jump up and have both feet high above the ground. Your feet will always stay close the ground. Think of it as the difference between dropping a rock into water versus skipping a stone across the top. Follow these tips to make the most out of your move.
1. Start with one leg forward and one leg back.
2. Shift your hips back transferring weight to your back leg. Bring your front foot slightly back.
3. Quickly switch your hips, placing your front foot in position to initiate your meia lua de compasso. Although you do both, focus more on quickly switching your hips than stepping into position. The fast hip switch helps generate power for the kick. Furthermore, even if you don't do the kick, the quickness of the switch allows for a fast and effective dodge using the entrance to meia lua de compasso.