For putting the seals on,
I have these sweet little hard plastic sleves that go over the top of the valve stem and then you slide the seals down over and in place.
They are about 1" long. When the seal is in place, just remove the sleve.
They are very thin, yet pliable.
I don`t know what they are called, I got them years ago when I did machine work.
Ck with your local machine shop, I`m sure they have them.