Liquitex Flow Aid breaks the surface tension of the arcylic paint. The paint flows better and dilutes in a way that your brush strokes will be less visible. It does increase transparency, but does not further affect the color.
Often 1 drop is more than enough to add to your acrylic paint. Normally, the ratio is 1 part Flow Aid to 20 parts water, so perhaps you can estimate what you need better.
Flow Aid can sometimes tend to foam with a lot of stirring, but then it's best to just let the paint go for what it is and then let the bubbles jump, you can then use the paint.
It is recommended that you do not use more than 25% of the Flow Aid in your paint because it may result in effects that you do not want, such as breaking the paint, poor adhesion or shrinking of the paint.
Only to be used for acrylic paints, not for example oil paints.