Its hard and you need to land on the pedal only to avoid hook ups that will throw you off. I still can't get them yet, ledges and stuff is not much of a problem as you can use your crank to grind also but landing and holding pedal only is difficult. Just watch a few videos you'll see how everyone grinds rails on just pedal, in fact watch 'this video' (http://tinyurl.com/2k9y9v) you can see him grinding rails on pedal ledges on pedal and crank. He is quite good though 😎
-- bungalistic
A COMMON MISTAKE THAT PEOPLE MAKE WHEN TRYING TO DESIGN SOMETHING COMPLETELY FOOLPROOF IS TO UNDERESTIMATE THE INGENUITY OF THE COMPLETE FOOLS
They usually have low rails to grind, so falling wont hurt to bad, and getting to do the grind wont be so risky.
Really though, just go for it, and land with lots of weight on the grinding foot. Too much weight on the other pedal can lose your balance, or twist the wheel.