They work very well if you have a good master to work with - and don't scrimp on decal paper. The best stuff isn't cheap but prints with very clean registration -he film is also very thin. Cheap decal paper has very thick film which looks "wrong" and invariably shows lines when the headstock is coated. The reason for sealing them with lacquer is simple: most end up coating the headstocks with lacquer, and with good quality film the finish lacquer melts just enough into the "seal" coat that the edges mostly disappear. Sealing them is done initially with 2-3 VERY light "fog" coats of satin. semi gloss or gloss lacquer (it doesn't matter which is you're coating the headstock). They barely even cover the decal - it should look and feel almost "dusty" after the first couple. Once it starts to look covered - but still not smooth - you go a bit heavier, with the last couple being fairly quick "flood" coats. Lacquer has very thin film build and the actual thickness of a flood coat is barely measurable when dry. When it's smooth you're done - don't worry about consistent sheen if it's going to be finish coated. Finish coating is highly recommended with inkjet decals as even the best ones are thicker than commercially-printed ones and stand out on the headstock. The problem with shellac as a finish coat is that it's very easily damaged compared to all other clears. Any cleaner that contains even a small amount of alcohol will act as a remover and smear the film - some window and other fast-drying cleaners (safe on lacquer & polyurethane) will damage it; so will prolonged exposure to mineral spirits & naphtha. Naphtha is used by most techs as a cleaner to remove grease, oils, sticker gunk etc - and if you finish a neck in shellac it can eventually end up a nasty surprise for someone. Because of this none of the techs or finishers I know use shellac on anything but historic instruments - violins, Weissenborn-style instruments and other vintage pieces originally finished with it.