First, you have to get a good entrada (step in) to the kick. When you take the step, really get a good pivot on your foot (step really far inside so the foot is facing the opposite direction), the more your foot is turned when you step in the easier it is to take off. Swing your arms to get good momentum when you step into the movement. After you step in, whip up your other leg and jump as high as you can. The most important parts of the parafuso are probably the entrada and the rotation. If you get a good wind up in your torso as you're launching, it'll be easier to kick your legs out. The entrada should start low and throw you into the air really hard with the help of your arms.
Keep the kicking leg straight. The first kick should be an armada. Really swing it high, it’ll help with the jump to get you higher into the air. As soon as you’ve jumped, the whip up your second leg (the one you did the entrada with) and kick it like a martelo. The first couple of times you do it, it’s okay to land on the armada leg first. But what you want to do is to be able to land on both feet at the same time. To work on that after you’ve got a basic Parafuso down, after you kick up the armada really whip your martelo. Try to stall your armada in front of you so the martelo can reach it. So basically try to get your second kick to ‘catch up’ to the first one. And keep both legs straight throughout the kick, it looks really sloppy with legs bent. Remember to get a good rotation in your arms, torso and kick as you take off. If you're having trouble getting your legs together, it's ok to bend the armada leg once it passes in front of you. When you bend it, you don't land on it so early and you can really work on whipping the martelo to catch up. If you want to learn one-leg parafuso, then try keeping the armada leg bent after it kicks in front so you have to force yourself to land on your right leg. You have to lean back in a parafuso because you can get your legs higher and swing them with more power. You don't have to lean back as far as possible, but you don't want to have your torso perfectly upright either.