OK Ryan -
I would start out by saying that you want to make each of those effects using two layers in your Comp - one for your text, and one for the mist/burn effect.
Put the text layers underneath your effects layers - Particular does nice smoky/mist effects, and pretty good flame effects. I tend to use Illusion (Wondertouch) for both of these effects when I do them, but if you've got Particular, that's what you've got.
For the mist effect, you could use the Shatter plugin that comes with AE - make your particle size very small, and use one of the shapes that doesn't have an obvious shape to it (bricks, glass, etc.). You want tiny particles to approximate the mist. When you've got your Shatter looking good, cross-dissolve it into the Particular mist effect, and let it dissipate.
For the burn effect, I would use the Erode plugin that comes with AE - play around with the presets - there are many that approximate a burn - animate the edge size to burn out the text, while increasing the flame brightness on the Particular layer. This will take some playing with to make it look as real as possible, but it can be done. Good luck!
Creative Director / Multimedia Specialist
B&S Exhibits and Multimedia