Sign paints are somewhat expensive. Exterior grade paints in small cans are your best bet. if you use one brand you can mix your own custom colors if they don't have it ready-made. You can use either acrylic latex (water-based) or enamels (solvent-based) but don't use both types in one sign. Use synthetic-bristle brushes for water-based paints and natural-bristle brushes for oil-based paints. Use a good exterior primer. Made sure your substrate is suitable for exterior conditions. Not all woods or plywoods can be used outdoors. Ext grade plywood is ok. MDO (medium density overlay) board is especially good for signs as it has a very smooth surface. ANy other questions, feel free to email me. ron