When i smoke rainbow i make a brine of warm water to dissolve the salt,brown sugar and soy sauce,a splash of tabisco,let brine cool.Also added apple juice say 1 cup.Depending on what you like salty or sweet I personally use 1/2 a cup of salt to a cup of brown suger.Keep skin on fish and put in brineovernight,move fillets around once or twice to get coverage in bowl and use a small plate to submerge fish.Before putting on smoker take out of brine andlay on papertowel,blot most liquid and wait 1/2hour flesh will get a shiney look now its time to put on smoker skin side down on grate.I like hickory wood chips and use a pan or two.Then leave in smoker until you get desired dryness desired,rotate the grates.I have a little chief smoker and have smoked beef for jerky and fish with great results.