Do connection/contact solutions work or not?

The BIG THING is to not use too much!
Whatever kind is used apply only enough to coat the surfaces. Usually wipe off any that will come off with a dry paper towel (Viva towels do not scratch)
The coating only needs (and should be) a few microns thick!
Too much is what degrades the sound after awhile. (a really big problem with too much Tweek)

Also, if you use it on male interconnects, a Q-Tip works wonders to slip into the slot between the pin and socket wall. (You may have to flatten the Q-Tip or remove some of the fiber)
(I have used Tweek, I now use ProGold)