TromboneChat

I have been doing this with my old Bach bass since the 1970’s and with the new metal valve linkages as I have acquired them. I put a gob of Vaseline on the metal sockets, then hit it with a lighter/small flame just enough to melt in the lube. Make sure the flame does not hit the bumpers. Once you get the linkage adjusted, You never have to change it. My old Bach bass is still quiet and fast. Also put a gob a Vaseline on the pivot and spring and hit that with a lighter. My Cerveny oval euphonium has linkage similar to the old Bach. It does really great this way too. I also find hitting the lube on a tuning slide will help a lot too.

The only problem with Vaseline is that its viscosity will vary greatly with temperature. In 45-50 degrees Fahrenheit, it will be very slow because the Vaseline will be rather stiff. If you perform on a hot summer day/evening and the temperature is in the mid-90s Fahrenheit, the Vaseline will be extremely thin and watery.

Many of the ball-joint and bearing lubricants that are on the market will maintain a more consistent viscosity. Almost all lubricants tend to thicken in cold and thin in hot temperatures. It’s the matter of how much they change that differs between products and brands.

Try using STP. I’ve used it on rotary valve linkages for years and it works great. Since it is a VERY thick liquid it is easy to get it into the ball joints and springs.

I just use valve oil on linkages, but if I were to go to some sort of grease I'd probably go in the direction of a silicone grease -- like Dow-Corning Silicone High Vacuum (which I use as a slide lube) or the poor man's equivalent of that which is "plumber's silicone grease" and can be bought in very small quantities at hardware stores, Lowes, Home Depot, etc. But I'm now thinking of going to one of the contemporary "dry lubricants" for linkages -- like 3-in-1 Dry Lube.

In terms of the flame approach, I'd be more inclined towards a heat gun or a hair drier.

I use a light sewing machine oil.
Thicker than valve oil & doesn't gum up like Vaseline/ grease.

I can also vouch for sewing machine oil. It's basically the exact same stuff as Hetmann #12 but five dollars gives you a bottle of it that will last you, your children and your grandchildren.

For the ultra clunky stuff like the old style Bach linkages I stuff them to the gills with plumbers silicone grease. There's one called "Super Lube" that like sewing machine oil will take you several lifetimes to empty. -Plumbers silicone greases like that also work well as tuning slide grease but they tend to dry out just a little bit faster than the real stuff.