If you can do fs 50-50s and manuals, you shouldn't have any trouble with the fs 5-0 – just lots of fun! Basically, you're doing a wheelie while grinding on the edge of the ledge, but it's actually easier than it sounds. You need to find a ledge that is lower than your ollie so that it is easy for you to ollie on and you can focus on learning the trick.
FS 5-0 - STANCE: REGULAR
Just like with the 50-50, you should ride parallel to the ledge as you approach it, with the feet in ollie position. Prior to the pop, crouch down a little and keep your shoulders parallel to the board.
Just like when you do a 50-50, you pop off with an ollie high enough to clear the ledge. Once you get to the highest point of the ollie, things are different from the 50-50. The back leg is stretched out and the weight is shifted off the front foot. That way, the back truck is lower than the rest of the board.
This is the position to start the grind. Make sure that you keep your balance so that you won't slip away. It's okay if the tail touches down during the grind – that makes the whole thing a little easier. Once you're feeling more secure, you can try to do the trick in manual position. But if it's okay for Rogalski (the guy in the pictures) to touch down the tail, then it's okay for you to do it too!
Hold this position in order to grind the crap out of the obstacle.
Once you reach the end of the obstacle, it's recommended to do a light ollie motion, but leaning forward is also a good way to land the trick safely. Bring your weight back over the center of the board and balance out the landing. That's it!