I find it more difficult going to the nose for some reason. I am a back foot dominant surfer so my balance is always weighted more to the rear which i think that plays a part in it. I can cross step back with no problem and feel like the board is sliding below me more than me walking back. If you watch longboarders that are really quick at getting to the nose and back, there is more of the board moving under them than them moving on the board. Its harder to do this on a large SUP of course. The half step that pono mentioned is key. Once you have momentum and you are committed to cross stepping its flows much easier but getting started can easily through off your balance.