Here are the pictures and result of the samples we made yesterday.
Today we have done two more samples where we mixed the fine sand into the white topcoat first before applying to the surface, and the second sample was sugar again but this time just sprinkling it over the resin without patting or touching it at all.
The result and our conclusion is that the sugar method is the best (without patting it) which produces a very even and nice rough surface without deep holes!