To ensure accurate ratios, place your paint measuring cup on a flat and level surface. Identify the mixing ratio required by your paint manufacturer on the side of the cup. Pour your base paint up to the first mark of that specific ratio. Next, add your hardener and thinners, filling up to the corresponding marks for that ratio. Finally, stir the mixture thoroughly with a clean mixing stick until it is completely blended and consistent. Never mix on an uneven surface, as this will lead to incorrect volumes and potential paint failure.