If your luffa are thoroughly dried, simply peel the skin off and shake out the seeds. Getting the seeds out is easier if you cut the luffa into 2 or 3 pieces. Makes them easier to use, too, when bathing, washing dishes or the car, etc. They are surprisingly tough. (luffa is often called "Mexican dish rag")
After all seeds are out (hard to do, no matter how you try) soak them for a few minutes in a mild bleach water then rinse them thoroughly and you're good to go.
Just remember to rinse them well after each use and they will serve you for a very long time. cora

Thanks corar ! Do they stay rough or do they get softer?