Paint additives are used to do one of two things: 1. Change the final product of your paint or 2. Adapt the paint to the current working environment based on temperature, humidity etc. Additives like flattening agents and non-skid additives are simply products that change the properties of the paint.
Interlux Flattener can help to reduce an extra glossy finish, and their No Skid Additive is a great top coat that provides footing on slippery decks. Japan Dryer can be added to some paints to speed the drying time, and Marine Penetrol creeps into the most minute crevices and pinholes present on any surface where ordinary paint and varnish cannot enter. There it dries to a tough, flexible finish, forming a powerful bonding film for paint and varnish making them flow in even the hottest weather, eliminating brush marks, premature peeling, chalking and cracking
Awlgrip offers a variety of paint additives designed to speed or slow paint dry/cure time, as well as 'Griptex' a non-skid formulation that can be added to the paint to yield a non-slip surface.