Which mobile shaders to use with Lightmapping?

I am able to successfully create light maps, but still feel uneasy with how the light map is actually applied and which shaders I should be using for mobile development.

When lightmapping for mobile, should I still be using specific mobile shaders to set up the bake, or can I use standard diffuse and other shaders?

Does the light map get applied on top of the currently used shaders, or does it replace them completely with some magical Beast shader? (In the Angry bots demo, I noticed that the light-maps contained color info and my current maps currently seem just to contain greyscale values, so this was adding to some of my confusion.)

Are there any guidelines for how big the lightmaps should be for mobile? Are they handled the same as regular textures in regard to memory, or are they optimized in someway?

Thanks in advance!