powerfishing guide 101
Build something like this
If you don't have the props or VIP you can also set them in the water near hicktown where the water shallow enough where you can still walk on it and the hook is fully submerged and a bit further in the water. If you have multiple fishing rods you can leave them and they automatically hook a fish for you, only thing you have to do is pick the fish up. Best way I found out how to do this is to raise the fish with your fists and spam E as you let go, get used to it and find how to do it perfectly won't take long. After that it's just collect fish from there, I don't recommend cooking all the fish just sell them all in one go. I also recommend getting storage chest(s) and a Ford Transit so you can store all your fish in there without any problems.
Oh, and don't forget to bring a gun. Just in case.