i dont have experience with tru-oil but from what i know it is similar to tung oil. tung oil doesnt have filling properties, it simply penetrates the wood, and successive coats build up on the initial coat. if the wood or whatever youre applying it to is grainy it would take many coats to fill, making it better to use something else to fill the grain first. tru oil works great on skins, as does tung oil. when i do mine with tung oil i scotch brite or steel wool in between coats, if the skins have a lot of the little nibs on the scales i sand lightly with some fine grit sandpaper until theyre gone enough for the tung oil to be smooth. with about 10 coats of tung oil they shine like glass, very good results. the stuff i use isnt pure tung oil its "tung oil finish" which is just tung oil mixed with a thinner. i think tru-oil is polymerized.