A 6x6" pole should be able to be walked up if you use light weight fixtures, or if you have a tree around and have some rope and rigging hooks and pulleys, For a long time we didn't have a pole setting truck, and or help, so I got pretty good at doing my own rigging, I kept a extension cord reel with about 250' of 5/16" hollow tube nylon rope on it, and had an assortment of quick clips and pulleys and various other eyelets hooks and stuff.
One thing to keep in mind also is when you dig the hole for a hand lift pole, remember to dig it a little deeper, because you will shave the sides of the hole as your walking it up.
I have raised up to a 10"x20' round pole by hand rigging, but I installed the fixtures after it was set by climbing with climber boots with tree spikes, I used a deer stand tree seat to sit on while using pulleys and the same rope to pull up my brackets and lights, which I had tied to several ropes to before I went up, what I did is I tied the several ropes to one rope long enough to reach the top, so after I got seated and tied off, I used this one rope to pull up the ends of the other ropes, I used a slip clevis so I could stop and take breaks as your arms can get tired, on heaver lights I would use my Greenlee hand wench which I would pull up before the lights, also befor you raise the pole make sure you drill a hole all the way through the top of the pole to put a eye through with a locking nut so it can't come out, they also make an aluminum jib boom that you can walk up the pole above you, so as your climbing you just push it up and it automatically locks in to keep from coming back down, this jib reaches above the top of the pole and can make the raising and mounting of the lights easier, but I'm not sure where to find one as I haven't bought one in years.
Ok I'll make another post to add more in a few after I get done eating