Naughty Cubster Actually I used a homemade concoction of beeswax and turpentine, working in a chemistry lab at the time was a huge advantage. Vaseline seemed the most readily available substitute. Warming or thinning it with something so you can paint it on would help.
RTV is an acronym for Room Temperature Vulcanising (i.e. it hardens without heat) - the stuff we used was a two part silicone we got from a company in London called Tiranti - I have no idea if they still exist.