The first thing you want to do, is to go out and catch yourself a fish. Now this fish can be of any size, as long as you think it is the best fish for you. If you feel that the fish which you have caught is of decent size, then you can start to think of painting with it, in order to record its measurements.
The first thing you want to do is to lay the fish flat on a table, you may put paper and newspapers underneath it and even use a towel to hold it in place. Now go on and dry out the exposed side of the fish, you need to dry this part out rather thoroughly in order to get the best results. Once this part is dried out, go on and apply paint to that side of the fish. Be rather specific with this and make sure you get the whole fish.
Now go on and hold a piece of paper on top of the fish. After you have gone on to make sure that you are ready to print the image of the fish, go on and press down on the side where you had applied paint on the fish. Be a little firm when doing this. Hold the paper in place for a few seconds, then pull it straight up.
Now you have a painting of the fish, which you made using a live fish.