Surface preperation is important. Scrub it clean of all dirt. Get a good strong degreaser from autozone, scrub it down again. If you want to you can sand the surface of your kayak to give the paint more to grab on to, sanding also reduces the shine from your yak. Paint choice: bottom line is no consumer grade paint adheres well to flexable surfaces, high impact and friction areas. Then the effects of sun light, salt, sand, mud, and temperatures will also punish the paint. So my advice would be to use cheap exterior house paint, and touch up the paint job often. I also wouldnt paint a detailed grass pattern. Instead, paint it like mud and muddy water, then use some type of portable blind, or even just a grass mat to cover up with.
You may want to try shooting some clays while in your kayak, might give you some ideas.
You may want to try shooting some clays while in your kayak, might give you some ideas.