What you need for the Parafuso:
You only need a 540 kick to get started on a parafuso. You do not need a double leg.
Learning the Parafuso:
If you have a good 540 kick, there is nothing stopping you from landing a Parafuso, because it's not any more difficult to land than a 540 kick. But the parafuso is much harder to make look good! A 540 kick is more forgiving, you can do a 540 kick a bit sloppy and it can still look acceptable. A Parafuso is not forgiving, any little bit of sloppiness in the technique seems to result in something that looks like garbage. The Parafuso is all about cleanliness.
How to Parafuso step by step:
Training the Parafuso
Training the parafuso, like most tricks, is all about trying minor variations. The above step by step guide is only one way to approach it. Try a side to side setup. Try to lift the first leg up earlier or later. Try it starting with a spin hook kick or crescent kick. Try to speed up or relax more in the setup. Try to change the setup angle. Try to wait a little longer after you jump, or speed everything up. Etc. Keep trying minor variations until something seems promising. A good way to do this is to use my tip on the Trouble Trick page.
Cleaning up your Parafuso
Wear puffy pants or puffy shorts, because anything that cheats the need for the legs to be together and straight in the aesthetic helps. If you wear skinny pants you still need to really butt the legs together, so these do not help much. If you wear normal shorts it's even harder. If you try the Parafuso in a neon speedo it's funny, but making a Parafuso look clean in a speedo is a real challenge!!
Point your toes. Really. This goes for all tricks but try extra hard on a Parafuso.
Get your legs together the right way
One of the things that makes a parafuso work, is bringing the non-kicking leg (the first leg to come up) far across. If you do not do this, you may notice a tendency to bring your legs together early and fall down with your chest low. This is exactly what makes this trick a bitch, because if you bring your non-kicking leg far across, your legs will come together either too low or too late, making it look retarded. If you bring them together too early you'll foul up the rest of the kick, and fall down with knees to chest as I've mentioned more than once already.
What can you do? The high road is to bring your first leg far across, but high, with full extension of that knee and toes pointed; And to kick OVER that leg at the right time instead of butting your kicking leg into it. To help accomplish this, wrapping your arms in after the kick instead of just forgetting about them will help immensely.
Upper body position in Parafuso
Amazingly, victims of paraconfuso can find remedial value in simply forgetting about the legs and focusing on the upper body entirely during a parafuso. Same goes for tricksters having trouble with the double leg (and 720 double, and many other tricks!). Get your arms to sling you up and then wrap them in like you would a 540 gyro. See my 540 tutorial.
Specific problem advice:
"I can't even land the trick! I can 540 fine and everything but when I try this trick I just crash into a heap? What happened?"
You shouldn't be crashing this move at all. Zero crashes. None! NO CRASHING RULE FOR PARAFUSOS! If you are, then you need to go back to the 540 kick.
"When I try it, my feet touch together early but it falls apart before landing! Its awful!"
Your kicking leg should not come off the ground until your non-kicking leg is way up and extended. And you should not butt your feet together.
"My parafuso only really looks like a parafuso at the very end of the technique. I don't like it, how can I fix it?"
If this is your problem, then you are very close. You just need to keep practicing; In particular, I think your best bet is to work on straightening your non-kicking leg earlier, and focusing on what your upper body is doing.
"My parafuso starts out looking good, but I land so short that it simply ruins the aesthetic of the trick. How can I prevent my parafuso from looking like a midget?"
This is probably an upper body problem. Many of my ParaFUCKUPs in the video above show this problem. What needs to be done is shifting focus to what your upper body is doing. Ideally, when you're up and parafuso'ing your legs together, your upper body will have one. fluid. motion. What you don't want to happen is to get stuck and fall out of the parafuso. Your arms and upper body should be working to maintain a healthy rotation through the end of the trick.
My experience with the Parafuso:
I landed my first parafuso late in 2003. In late 2004 I figured out a better way to do the trick, (kicking over the non-kicking leg instead of making the two meet) which made my parafuso look great! In 2005 I had trouble with the trick again! I couldn't get that good "double leg look" again because my setup stopped working. A year later I learned that the side2side setup made the trick incredibly easy, and that made me think deeper about its mechanics... So deep that it ruined my Parafuso for quite awhile. I decided the parafuso was just a finicky bitch and that I hated it. After I was done being hateful, I upgraded my 540 kick by becoming more intimate with the wrap, which ended up fixing my parafuso forever; This fixed my parafuso because it taught me the importance of maintaining a healthy spin with my upper body during the trick. Now I parafuso happily ever after. I recommend reading my 540 kick tutorial too, if you haven't. Between this tutorial on the Parafuso itself, and the tips in the 540 kick tutorial page, you will parafuso happily ever after too.