I'm referring to layering effects during compositing - not Maya's "layering".
At any rate. Duncan's Blog shows a method using Fluids - which gives really organic, soft billows:
area.autodesk.com/forum/index.php/blogs_duncan/blog_detail/simple_moving_fireball_with_maya_fluids/
3DBuzz also did a fluids training series for Maya, in which they build a fireball plummeting toward an ocean - see attached video (though they don't show you how to create the actual impact):
http://www.3dbuzz.com/xcart/product.php?productid=15You could probably do a decent meteor with particles as well - using the surface of your meteor as the emitter(s) - but will take quite a bit more work to get the same dynamics you get using a fluid.
17295_kxgYvocwvRTAzef5ilJq.mov