If I had a stiff Girdraulic I would drip some oil on the moving joints of the links. Maybe a few days in a row. Then, one day I would put the floor jack under the engine while it is on the rear stand and lift the front end off the ground just a bit. Look to see if the front mudguard or the mud guard stay is too close to the mag cowl for comfort. Assuming the clearance is fine, you will be able to move the bike up and down to check that it is attaining full droop (the fork droop is limited by the damper travel) and that it settles down well when you let the jack down. You should get maybe 3 inches of jack movement.
If the fork looks and feels like it is still resisting settling down, it is probably the springs that are too stiff. They were pretty much too stiff from the factory and yours may have settled a bit over the years.
The answer to the questions in Vibrac's post will lead to much more specific advice.
Ultimately, I like the fork to settle down a total of about 1/3 of its movement, which I measure on the damper, when seated on the bike. The damper moves about three inches, so an inch of travel on the damper is the minimum. I have run my racer at about 50% of travel, but the tracks are smoother than the streets. Anyway, the less loaded sag you give the fork the taller the bump you can absorb. That is the compromise you are trying to negotiate. This is pretty much the same as a modern tele fork. The travel is longer, but the percentages of travel and sag should be about the same.
I put a zip tie around the damper rod to measure the movement. At some point you will want to see if your front damper is functioning, and you can do the same by leaving the damper cover off after you have removed the damper to test its resistance.
It takes a while to make friends with the Girdraulics. Even with problems, the forks will probably work around town, but the lack of comfort may be the limiting factor. A photo of the links and damper would be helpful.
David