I created something last week that looked very good. I did not use it as a transition, but it could easily be a transition. I wanted to burn a hole in a book page. I just laid a large piece of white poster board (I did not have black paper around) on the snow, poured a little circle ( I needed a ring of fire)of gasoline on it, turned the camera on & lite the fire. I videoed the fire from the same perspective that my 3D comp camera was in. I masked out and feathered the areas on the fire video that I did not need. The white paper matched my book pages perfectly. I also used CC Page Burn to reveal the page underneath. For a transition, you could use CC Page Burn to burn off the entire page.
The entire process took 15 min. I spent more than that much time searching the net on making fire in AE.
I am still looking for a good fire tutorial.