What type of paint works well on plaster? So, the color of my dyed plaster died. After I finish up the details and smoothing of this piece, I'd like to restore the color with some paint.

What type of paint will work well for this?

I need something that will:


Hold fast
Work easily on the semi-porous plaster
Not seal in moisture in the piece, or add to it
Preferably semi-glossy to glossy
Not smooth out my fine edges and detailing, or thicken/round them
Since you don't want to loose any surface detail in your casting and it's a porous material you are wanting to colour, have you considered using a dye or stain instead of a paint?

Using dyes, you chemically change the colour of your material. Adding no thickness to the item being coloured.

I don't have much experience with dyes other than colouring Easter eggs. Using melted wax to mask areas allows for ornate designs to be created. 

Here's a demonstration of the process.