Ok, you have 2 choices here, frying and deep frying. I’d say deep frying isn’t worth it over a camp fire, you’ll never be able to keep the oil at a good temperature, and you’re more likely to end up with a flaming pan of oil than properly cooked fish. It’s not really deep frying if you don’t have enough oil to completely immerse the fish anyway, it’s just frying with too much oil if you don’t have enough.
So for regular frying make an egg wash, 1 egg stirred will into 1 cup of cold water. Pour the wash over the fish in a bowl or in a plastic bag, make sure all the fish is well coated and sits in the wash for a few minutes. Make a breading mix out of 1 cup flour, 1 cup fine bread crumbs, and 1 tsp of baking powder. You can add a couple of tablespoons of corn flour for more flavor and crispness. Put just enough oil in a hot pan to fry with. Take the fish and roll and press into the breading, then lay pieces of fish in the pan. Add small amounts of oil as needed. Cook 1 - 2 minutes on a side, then turn and cook through, pulling pan off the fire to reduce the heat if takes more than another 1 - 2 minutes. Cut the fish thin to reduce the cooking time.
If you absolutely insist on deep frying, make a batter using 1 cup of flour, 1 tsp baking powder, and 1 tbsp corn flour, you’ll need mix up several times this amount. Keep the fish moist in a covered bowl or plastic bag. Mix a batter out of the dry ingredients and cold water that’s slightly thinner than pancake batter. Dredge pieces of fish in the dry mix, then holding with your fingers, dip into the wet batter, then lay the batter fish into the oil holding one end and moving the fish for a few seconds to keep it from sticking to the bottom. Lots of bits of batter will seperate and float up on the oil, remove those with a skimmer or slotted spoon. The fish will float up in a minute or so, turn to cook evenly.
You can’t do anything about coated fish absorbing oil, but keeping the oil hot enough will reduce it. You can mix your dry ingredients ahead of time, just keep them dry. For dry coating make sure all the ingredients are well mixed.
I’ll make an appeal to authority here, my own, I’ve fried over 20,000 pounds of fish, I have some knowledge of this subject.