Most of us here are not going to be familiar with tropical grass care (although you might get lucky!) so I'd check with a local source to verify anything said!

However, Manila grass is Zoysia matrella. I'm not sure if the Manila grass is your grass or if it's the weed in your grass. Could you let us know? Zoysia's hard to get rid of it's a weed (it happens sometimes up north if your neighbor has it and it starts to grow into your lawn).

If you just have weeds in your Manila, that's easier. Feed monthly during the growing season with any good nitrogen fertilizer--we want the lawn to form a dense growing mat that will cover the ground and provide fewer spots for wees to sprout. Cut as tall as you can stand it, taller cuts shadow out weeds. And water as rarely as you can get away with during dry seasons and periods to keep weed seeds from sprouting.