I found vasoline to be more longer lasting than cooking oil. Takes more time to rub it into all of the nooks and crannies but it is much thicker. Soaking their legs for a few minutes is nice too, it is way cleaner for the one applying the vasoline. I also take a piece of paper towel though and dip it in cooking oil and rub the roosts down. I have been unsuccessful of eradicating the mite problem over the past 2 yrs so with 34 chickens I have just decided to control it with natural methods. I prefer that to treating with a drug that is not approved for chickens that has no definate egg withdraw guidelines. I would use the systemic drugs on a pet chicken or retired chicken though. As long as scaley leg mite is controlled and you keep their legs in good shape with lots of "spa days", you have nothing to worry about.