Did you know that regular human shampoo and conditioner work just fine? Wig fiber is ridiculously tough stuff. Just swish it through a sinkful (or bucketful) of cool water with a squirt of shampoo in it and you're golden.
You can put on conditioner the same way or by diluting it and using a spray bottle. Conditioner is really only needed if you're detangling, though. Plastic doesn't need any conditioning.
Tom Petty [Final Fantasy XV] (9%)
Bondage Finch [Bondage Finch Adventures] (12%)