Find a metal beam and a large room, grab onto one end of the beam and start swinging in the air. I found it easiest with a clockwise rotation, so I would start by swing the beam anti-clockwise until it was parallel with the floor and then swing it back the other way. The momentum should carry it round and the beam will push your character round for one spin.
If you keep the momentum going, four rotations in succession should be no problem - after some practice.
I've seen some people do this in the big room that's bottom left from the 'Heart Room', but I did this in Extended in a room with a magnet.
You should also be able to do this in the large cavern with the furnace - when completing the puzzles in the rooms to the left of that cavern, the last puzzle will require a metal beam. Just bring that with you out and completing the spins in this cavern should be the easiest place as it is massive and it should be much easier to avoid walls.
This video from "aka Scratch" demonstrates the achievement.