Good quality feed and some Vitamins Electrolytes Plus might help them overcome lethargy. The poor birds were obviously neglected.
That has to be the worst case of scaly leg I've ever seen. It is caused by mites that burrow under the scales. My Dad had a rooster with a bad case of scaly leg. With regular soaking of his legs and feet in Linseed oil, it eventually crumbled off in a few months. The sprays sold which drip off the scales and don't penetrate under them aren't worth a dime. Rooster Booster makes a product called Sulfur Ointment that I've found works very well on scaly leg. Use medical gloves and massage it gently all over the legs and feet when they first get in to roost at night. I'd do it every other day until you see improvement. Use Ravap, or an emulsified concentrate Permethrin, and spray or brush your roosts with it in addition to the whole poultry house. This should be done after the house is cleaned of all shavings and disinfected with Oxine or a phenol like Biophene. I personally like Oxine better for regular use and disinfect/pesticide my coops every three months after all shavings and dust are removed. Chickens are only allowed in after the housing is dry. The best time to do it is early morning while the birds are outside ranging.
Dipping the legs in a container full of oil seems more difficult. One has to endure a few minutes of holding the bird and keeping it from spilling the container and flapping oil all over the place. If your bird is very docile, you might prefer doing that. Let me know how it goes. If you have any questions, feel free to ask.
P.S. Whoever sold you those birds is a reprobate if he/she didn't alert you to the bird's condition.