Obviously let it dry first, then use fixative spray? Not that I'm an expert. Or make finding the preservation part of the artistic process. Alcohol? Lemon juice? Ashes? Lime?
edit: what are you planning to paint on?
BTW painters of centuries ago used lots of organic materials even from animals, might want to check out if they had some tips.
A Hobby Lobby canvas. Since Joann died and Micheals is far more expensive, I’m occasionally forced to resort to them. I make sure that a good portion of my art work is profane or has explicit political messaging to even out the karmic energy.