If it's just an ordinary splint, you will basically recover after washing it once or twice. After all, the two methods are different. The former is a physical and chemical change, while the latter is only a physical change. Of course, the price will vary a lot.
If your hair is naturally straight, just pinch it normally. Even if it is deformed after washing, it is only a small deformation. Don't use lotion or perm, which will damage your original good hair and lose your natural feeling.