Sometimes we get what we pay for. I bought LandPride forks, yeah spendier than others and they work and adjust jes' fine.
I don't remember what brand my forks are but I found if I release the top pins, have the forks about waist high and tipped slightly down, I can just lift slightly with one hand at the center of the forks, then use the other hand to slide the vertical part. Doing it that way they move fairly easy.
I also raise my loader a bunch and point the forks almost straight down. This relieves the pressure of gravity and they slide easier
These are the way. -- With the cantilevered weight relieved in this way even standard WD 40 will be very effective assisting the slide. And the application is clean and temporary.I don't grease mine, just attracts sand. It helps if you unlock the pins so the forks can slide. Then raise the FEL and point the forks straight down... When you get them close to where you want them, release the pins so they can pop back into position. Usually move easier in that position.
I added a hydraulic fork positioner to my tractor works great.