Start by cutting your pipe to size. I have my tiki masks cut to about 17". You will want to make sure you have some blank space on the bottom of your pipe to make sure you can "hide" the light from peeking through the mouth opening.
To give my pvc pipe more of a "wood" look, I used a utility knife to sort of "rough up" the pipe by scraping lines into it. I just went up and down the pipe in no particular order until I had it full of lines.