Hello and welcome to the shipyards!
As far as what paint to use for your customs, the usual medium of choice is acrylic model paint.
I use testors, model master, and floquil acrylic paints and many others use citidel games workshop paints.
As far as detailed markings, some people use a mechanical pencil to kind of sketch the markings on a figure prior to painting them. Some use decals, and some just do it freehand.
For your first project, start with something simple and as you go along, your skills will grow.