What kinds of paints should be used?
Basically, there are latex (water-based) and alkyd (oil-based) paints. The former can be used on wood, stucco and concrete; the latter on metal and utility doors. Acrylics, which are bonders, are added to latex. The higher the percentage of acrylic the higher the quality of the latex and the higher will be the price of the paint. If specifications do not specify the percentage of latex, ask the contractor exactly what he is using; otherwise, your competing contractors will not be bidding apples to apples.