once the shoes get soaked with oil it is very hard to get all of it out and if you try and reuse them the oil embedded inside will ouze out when they get hot and you'll be right back in the same boat with no brakes because of oil coming out of the shoes and getting on the drums.
Years ago we tried many methods to try and reuse the shoes but once the oil gets in them it ruins them, we even tried boiling them but that broke down the bonding and also weakened the material considerably and the shoes fell apart after a short period.
It is always a better idea to go ahead and get new shoes period... it's not worth the time and trouble to attempt to try and save the old oil soaked ones, you'll never get ALL the oil out of them.