First thing is get flate blade screw driver, use it to turn the stem back and forth. As you do this add tiny bit of pressure to lift handle. This will get the stem or plunger end to mate better in the spout. I don't know what JW did to his but you can actually get a small tin of valve lapping compound and after every thing is good and clean add a little of the compound to end of stem and do same process. It will cut the metal better and give you a more precise seat. Also I have found taking the screw driver and turn the stem back and forth until it centers the slot in the lifting wire helps.
Proud Member of Team Geezer
Charlie Weaver USN/ENC 1965-1979