u wanna open the top use a hack saw. band saw also can.
if u wanna season the top, everyday cooking spices would do, garlic, ginger, sesame oil, ground white pepper, corn flour.
if wanna condition it to withstand singapores high humidity u should put ur guitar in a pail of water, after that im sure it will find the air very dry.
haha that was just in jest. as said above, the best way to do this is to constantly play the guitar.