I can tell you exactly how rest finger to open works on my old 5s which doesnt have raise to wake.
If the screen is off I have to physically press the home button once then I leave my finger resting on top of the button as the screen turns on and it then unlocks the phone.
So to recap .. I press in the home button once and leave my finger on top of the button while the screen comes on and then it takes a second for it to unlock.
Cheers