If cleaning up with a washcloth or just bathing did not occur to you, you must be looking for a more comprehensive answer. So how about letting more sperm land on you day after day, and let it harden and build up to a thick crust that covers your body. When it is so thick and stiff that it restricts your freedom of movement, thrash around and break it from your body. Push yourself across rough ground to dislodge the loose pieces clinging to your skin. This is how snakes shed their skin when they grow, so it should work for you also.