There is a product called Sedgehammer that is supposed to get rid of nutgrass without harming turf, but I don't know what it might to do myoporum.

Sedgehammer is extremely effective against nutsedge. But it will also kill a variety of broadleaved weeds as well and I'd have my doubts it could determine any difference between a desired groundcover and a common weed.

In cases like this - nutsedge growing in the midst of desirable, non-turf plantings or a groundcover - digging out the sedge, carefully removing all the nutlets, is the suggested method

I have this problem with oxalis...it is a painstaking process but as noted, it's really the only way to go. It's when an Agave gets over-run with oxalis that I am stymied!

Oh man that is what I was afraid of.

I generally don't like to listen to anything when I am gardening except the outdoor noises but last year I had so much weeding that I eventually gave in and started listening to recorded books while I weeded. It did make the time pass much more quickly. But an odd result is that now certain areas of the garden bring certain books to mind as soon as I am in them!