So all I really need to know is:

Can you use water based dyes with Mahogany? I'm concerned that it's so porous that the water in the dye will damage the wood, should I use alcohol for this?

Do you grain fill before or after dying? Most people seem to say after, but just making sure.

I have used water based dyes and they are fine..the idea is just to not soak the wood

always stain before grain filling because the colour won't penetrate through the filler if you do it first