Trying to do it while head on the car.
Not the best video but this is how I did it on a car:
Generic "overhead" tool that I then cut the bar down so I could run is along the short side of the block instead of working long-ways. Why? because you can't use the lever action of the handle as you get to the rear cylinders when working long-ways. You end up hitting the strut tower with your hand before pressing down on the valve spring.
This tool cost me like $40 on amazon and it worked pretty well once modified. Not sure if there is something "better" out there or not.
here is a similar kit:
Buy 8MILELAKE Valve Spring Remover Installer Car Engine Overhead Compressor Tool Kit OHV OHC: Valve Train Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
I know people claim the devices that you smack with a hammer work well, but, I can't see that working with how tightly and recessed the valve springs are tucked into the N5x cylinder head.