Black tank valve sticking

Lube, Spray,Blah Blah Blah been there done that with 3 of my 5er's ya just gotta buck up and replace the valve and cable before it breaks and like was said before use plumbers grease on the the new valve blades,I use Valterra like these : https://www.amazon.com/Valterra-TC372-Flexible-Cable-Valve/dp/B002N5L9R8/ref=sr_1_2?ie=UTF8&qid=1478416546&sr=8-2&keywords=valterra+waste+valve+with+cable as they are way better than stock ,it is not that big of a job just drop the underbelly and there they are and depending on you model just take out one of the walls in the basement area/Convienence center to get access to the back of the pull handles to remove them,there are also You Tube Videos on the subject that will help ya on your first one,BELIEVE ME you will like the results of putting in the new Valterra Valve/cables