If I am not mistaken, I think in the old times they used castor oil and sulfur to treat scabies, not together but they were seperate treatments that were used, the castor oil would indeed smoother the scabies and sulfur is still an actual scabies treatment that is very effective.
P.S I do not think anyone has used castor oil to treat scabies for decades, but I know in conjunction without other treatments that people use that real thick vaseline on problem spots as it is very thick and has smoothering properties. My advice would be to get some vaseline (the thick stuff), some sulfur creams and lotions (the banners on this forum) and then some epsom salts for post scabies to help your skin start to loosen up and let the dead scabies mites and their debris up and out of the skin.
Hope this Helps.
Pam