For IOS, design the buttons as plain, without rounded edges and no gel effect. IOS will by default add the shine and round the corners. There is no special skill required - just make them the correct size.

It is helpful for IOS to do the donkey work, because then we don't have a panel of icons that don't quite match in style. At least this way around the gel effect is uniform, as are the corners.

As has been said, you can do the gel effect if you wish to, but it's not a sensible thing to do in this context.