Oils are basically artist paints that are bought in tubes Paints are a balanced combination of a colour pigment and carrier. Most paints come in little jars or tinlets. Testors have a range of acrylics that are stored in a small packet. When painting, the carrier acts to slow the drying time for the paint, giving the user time to apply the paint from the tin or jar to the model surface. Drying time is also dependent on the weather conditions.
Weather conditions can affect the paint.
An extremely hot day can dry the paint a lot faster, thus drying the paint in the open tin of paint and a humid day can increase the drying time. The type or brand of paint to use is more of a personal thing. This article looked at several different brands and the advantages and disadvantages of using each one. Scale modellers are generally 'cheap' hobbyists. That is, we try to revive 'dead' paint for a model to save money.