Typically, we say to use a 1:1 replacement for Silicon Dioxide. If the product is very oily, you may need to use more Nu-FLOW. Typically, customers use 0.5-1%. As you look at the formulation, caking will be caused by either oily ingredients or hydroscopic (moisture absorbing) ingredients. Once you identify the problem ingredient(s), blend the most problematic ingredient with Nu-FLOW first, to get the desired flow properties. Then add the other ingredients. You may want or need to add a touch of Nu-FLOW for insurance. As the moisture or oil equilibrates into the Nu-FLOW, the flow properties will improve.
If Nu-FLOW is not solving your problem, consider Nu-SORP