We recommend this polish because it is not a wax based product and has a longer life and is easy to use. For applying Nautical Ease polish use a cloth that has some texture to it such as a clean untreated shop cloth or a wash cloth type material as opposed to a tee shirt or a diaper material. The textured cloth will help clean much better as it gets into the pores and doesn't just skim over the surface. And no, it won't scratch when used with the Nautical Ease polish either on a boat or a car. There are a number of variables in answering this question.
Most boaters apply at least a couple of applications of finish at the beginning of the season.
If you trailer your boat and store it inside or outside and it is covered completely, a couple of coats are all you would need for the season. If the boat is stored outside uncovered or partially covered an additional application per month may be needed to give it maximum protection from the sun. In the extreme south where it is hot and the boat is used all year long, it will be necessary to polish it more often to give it the protection that it needs. Sun and heat are the culprits when it comes to damage to gel coat and the life of the finish. Then again, how particular are you about how your boat looks.