Happy to. This is how I do it and it works every time. Get a good penetrant, I use Gibbs. Spray it on the valves stems and let it sit there for a few hours at least. Put the knobs back on the stems and start working them up and down and left to right until they loosen up and they will eventually. Then I put a brass wire wheel in my drill and polish all the stems until they are nice and shiny again. This helps with keeping the valves smoothly working. Finally, turn the manifold upside down to let all the excess penetrant leak back out of the manifold. Wipe it all down and you'll be good to go. The only variable is really the time it takes for this all to work it's magic. I've let the manifold sit for days like this while I work on the rest of the grill so don't be too impatient.