subject="Some of my learnings"
I've had a go at installing NetBSD on a Macbook Pro (mid 2012 model). I'm using NetBSD current as of 2016-10-25.
The NetBSD installer from current can install to the whole disk, but it doesn't use GPT. Regardless, it boots ok after a ~20 second delay. In order to remove the delay, I've followed the above instructions.
I had issues with running newfs_msdos from NetBSD. I rebooted to MacOS recovery ran newfs_msdos and then did the rEFInd install.
Assuming that rEFInd has been installed, when changing to hybrid mode, GPT fdisk now has a EFI module that can be copied to the EFI/tools directory. Then you can run gdisk directly from rEFInd. There is, now, no need to install MacOS to a USB stick.
The instructions seem to leave out installing the bootloader on the NetBSD slice.
CVSweb for NetBSD wikisrc <wikimaster@NetBSD.org> software: FreeBSD-CVSweb