The bantam in my avatar had a big case of scaly leg mite when we purchased him last June. The scales were rough and raised like tree branches. Both the tops and bottoms of feet and deep cracks need to be well saturated evenly everywhere, and that's hard to do with thick product like Vaseline.
What we did was dip him in mineral oil in a cup daily for a month, touch up especially bad areas with deep cracks with Vaseline, then "flour" his legs with DE, so he stalked around with white 'boots.' However, he walked MUCH easier when we did that, and the oils didn't get all over his feathers when layed down or he was on the roost. He also quit slipping off the roost at night too.
It too about 4 months to get the yuck completely sloughed off. His legs look great now. We still touch him up from time to time (as he is part of our free ranging group) and we can watch their legs, to make sure everyone stays leg mite free.
Good luck!