If there any substance -- for example, a deodorant or lotion with a specific ingredient -- which would allow drawing a picture or words on your body for the scan-reviewers to see?
I believe I read somewhere that research into tHz-blocking clothing was done along with the development of these devices. However, I doubt we'll soon see a booming market for metalized underpants in the duty-free zone. I too have thought about sending a harmless message through the scanner, but came to the conclusion that it wouldn't be worth the inevitable harassment.