The pig oil is just a light oil which provides a barrier to water and helps mud and things sticking to the feather (or mane and tail). Flour of Sulphur is a yellow powder which is used to get rid of various insects, gardeners use it as well. Its used to stop leg mites in horses with feather.
Either of them will work on their own, although the powder can be difficult to apply and will come off quickly.
Mixed they are used by the heavy horse and M&M people to stop mites and go some way towards protecting against mud fever and stop mud caking in feathers. Its greasy but does wash off easily for showing. Its not good in summer on the mane, tail or body as can cause sunburn.
In my experience its not brilliant if you already have mites, but once you have got rid of them it prevents reinfestation.
If I use it I put it on clean dry feather every few days and dont wash the legs off when they come in.