I don't know what competitors do but, imo, you want a sheer finish. What I do sometimes: I heat a little good strained homemade light beef stock with a little unsalted butter, mix well, then paint it on the slices (you could dip them but I like to avoid the bark area). Alternatively, if no homemade stock is available, mix store-bought beef stock (get the best you can find) with low-sodium chicken stock. Store beef stocks are often a bit tinny, the chicken stock helps to eliminate that and it lightens the color a bit, a good thing, imo. A 50-50 mix is a good starting point. Add a little butter, heat til the butter is melted, mix well, paint on immediately after slicing.