Hey Old,

Let's try something.

Sand down the edges of your patch, until they are rounded and smooth, not square and stands out.

Now from a craft store or even Walmart get a cheap set of pastel chalk. Scrape the colors of chalk you like to make mud, dust, and dirt.

Mix in some white glue. If you want wet looking mud also mix in some acrylic floor polish. Make a thick yet workable mud and apply to your tan to cover the patch and other parts of the hull where you will find mud and such.

Don