Try sulphate paste or a mild solution of creosote carful not to get it on the skin use a stiff brush to work it in, with in a couple of days the crusty scales will drop off giving you a clean leg, Scaly leg is caused by a mite which love very dry and dusty conditions so the litter needs changing before it gets to that state, perchs need a good washing and then painted with creosote or a similar solution the cote can be washed out with a good disinfectant
i used to use an ivermectin spot on with good effect. as with all insecticides it is vital that you repeat treatment after 3 weeks because most of them ( ivermectin incl) will only kill the adult stages and not the eggs. almost all of the ectoparasites affecting our domestic species will have an approximately 3 week life cycle so hit them twice. now i use equine hoof grease! it sticks really well and coats the legs for days. if you want a belt and braces approach i would treat with frontline spray ( USE GLOVES AND WET THE LEGS THOROUGHLY) and then coat with vaseline/sudocream/hoof grease/udder salve and then repeat the whole process in 3 weeks.
we are having a wet winter so to keep them away here i use brown vinegar on the legs just watch your eyes how to do it with an old tooth brush pour some vinegar in a cup don't dilute it it takes about 2 days for the mites to be gone and the legs clean after the mites have gone i wipe the legs with some vaseline
for the pens i clean them out wash them out with bleach let dry in the sun if you can if not let them dry spray with a a good surface spray. do all you pens with it or i do my night perches you have to do them every 2 weeks till you are on top of them and every month when you do you clean out re spray with the surfaces spray angie