The only reason to oil strings is to keep them from drying out. If the air is humid enough most of the time, the strings will not dry out. Unless you keep your bass outside in a very dry climate (which you wouldn't want to do even with steel strings), oiling gut isn't necessary.
If you are oiling, you do not want to soak the string with oil. If oil soaks into the string, that will result in false intonation because you are actually changing the string's mass in the oiled area.
Using alcohol after oiling defeats the purpose of the oil; alcohol is the universal solvent, so it could end up drying your strings out (resulting in the need for oil!).