Brook trout have no no-:iceable scales, but they should be scraped free of slime. Rainbow trout need scaling.
Remove the vent, cut the gills free from the lower jaw and back of head, and slit open from nead to anal fin. Draw the inside out by the gills, and scrape the clotted blood away from the backbone. If the fish are only for the pan, not to be exhibited, cut the heads off; then they are easier to clean. Large ones, anyways should have heads and tails cut off before frying.
A small trout may be cleaned without splitting, by cutting out the vent, tearing out the gills with the fingers, and drawing the entrails with them.