Hello, fellow film worms!

I'm a new guy here looking for some help. I'm helping a friend of mine with a horror/slasher film he's aspiring to make. And I want to have that "burning title effect" a la John Carpenter's "The Thing".

It can be viewed at 1:43 of this video - http://youtube.com/watch?v=KG10O204lEg

imdb.com states....
To create the effect of the title, an animation cell with "The Thing" written on it was placed behind a fish tank filled with smoke that was covered with a plastic garbage bag. The garbage bag was ignited, creating the effect of the title burning onto the screen.

Has anyone tried this before? Does the garbage bag cover the whole fishtank? Or just the top rim?

Any helpful replies are appreciated!