I wash mine out with Dawn after I use them, then they go in with my MF towels and get machine washed. Although they seem to be clean after machine washing they never do return to that bright yellow state, it's more of a greenish yellow color. I've tried presoaking in the same stuff I clean my PC pads with but it doesn't seem to help much. I might try machine washing some before use just to see how it works.
Good idea to put an applicator that's going to be reused with the same product in a sealed bag whether it's washed or not.
While they are relatively inexpensive it seems kinda wasteful to toss them after use. Like worn MF towels they could be delegated for grunge duty. Depends on how many a person uses I guess.