There are many ways to go varying from 4th class to easy 5th. I went directly up the large gully in the center left. If you are going to climb the Fatiron, you should consider adding this to your climb, you're already there anyway. A lot of fun on good rock. If you have a pack and don't want to carry it up the Fatiron, you may want to down climb the gully to the north between the Fatironette and the Fatiron to leave your pack for retrieval at the end of the day. Easiest descent from the top is over the highest point with the shrub. As a destination this would be a stunning place for a picnic, just don't drink too much wine, you still have to down climb.
Below the first piece of the Fatiron.
Free Solo... but would protect well if you feel the need.