As long as it takes. Might seem a daft answer but each stock is different . One may look great after a few applications others take longer and there is nothing more annoying than that one patch that will not seem to finish as the rest does .
I have been using Trade Secret for years , not just that a good friend makes it but because it suits me . I tend to add a couple of drops of Terebine to a small amount of oil on a saucer ,just enough to use as it speeds drying time and when you may have 5/10 stocks at a time it all helps .
