This might help.
Webbing Solution 1 Pint- A resin based additive thats added to gelcoat at a ratio of 2 parts gelcoat to 1 part webbing to achieve a "web" effect. Used generally in the second coat after applying a solid primary coat. Decorative effects produced by the webbing mixture will vary, and relate directly to techniques or gun adjustments. A fine hairline spider web pattern results from plenty of air and scanty material flow. Coarse and splotchy patterns are created by fuller material flow and decreased air volume. Experimentation will help determine the desired effect. Item: 2040
Supplier of webbing solution
I have not used the product, this is just something I knew about.