The locals dealers here leave it all soaking in the sea for a month or two which they say makes it termite proof.. We still strip off the skin and stain the whole length with used oil mixed with new oil (for desired stain tone) as the flying termites (bok bok) cannot tolerate it. Once the bamboo has seasoned for 6 months the little #$@@@#`s are no longer interested so its time to varnish. I thought that there was no way they would bore a hole through a new piece of bamboo with 3 coats of varnish on.. I was wrong. Some holes were the size of a 1/8 drill bit.. They move in through these holes and then through the segments laying eggs that hatch and eat everything from outside in.. Destructive little #$@#$#`s.
One of the things I noticed about using used engine oil for wood preservation was that it never actually dried out completely, even after a year or so. But that was in the UK and not in the Philippines.