Running out of paint is one of the worst things that could happen when you are painting your gunpla. It's even worse when your local hobby shop runs out of stocks and could not tell you when the new shipment will arrive. So I hoard paints. Lots of them.
There are mainly three types of paints used for painting gunpla: Acrylic, Enamel and Lacquer.
Acrylic paint: Considered the "weakest" of the three. It has the longest drying time and curing time. But once it's fully cured, it adheres very well to the surface of the kit. I mainly use acrylics when I want to give my gunpla a flat coat. For gloss finish, it's better to use enamel or lacquer. Another reason why some people prefer this type of paint is because it's the least toxic paint.
Enamel paint: This kind of paint has shorter drying and curing time than acrylic paint. The most readily available paint in the market is Tamiya. It uses enamel or lacquer thinner. The smell is always a turn off for some but it does produce quality finish.
Lacquer paint: The most toxic paint and unfortunately my favorite. Lacquer paints produce high quality paint finish. If you're gunning for that high gloss finish or realistic metallic finish, then lacquer is the way to go. This type of paint has the shortest drying and curing time. The paint dries upon impact on the surface. This is not recommended for hand brushing unless you have a leveling thinner and a retarder with you. Don't forget to wear a mask!
Happy painting! :)