Regarding HAND washing - one can soak items in a sink or basin and swish items back forth occasionally. Agitating is what makes seams fray. Then roll in a towel to blot out some of the moisture and lay out on a flat surface to dry. Sometimes one can smooth out a lot of the wrinkles by hand while the item is still wet.
I think there are producdts available specifically for old textiles, but I have not used them. RetroClean may be one of them???
The older I get - and I am getting pretty old - the more selective I have become in deciding what is "worthy" of being salvaged/rescued.
Sometimes the items just aren't worth the effort. There probably is a reason why the project was abandoned before it was finished.