For additives that are used sparingly such as ring free, pick up one of the hollow medicine spoons that are used for giving your kids liquid medicine. It makes getting the exact amount easy and it is easy to pour into the tank regardless of the angle of the inlet tube. It works great and you dont end up spilling it on your gelcoat. An added bonus is that they are very small and effortless to store. Slap it in a heavy duty freezer ziplock and keep it in the bilge area.