Last set-up I did was 3 sections of 25G for new OTA/TV antenna.
Many times Used or New, the galvanizing "beads" up at the end of the couplings.
I take a large Uni-Bit and reamed that edge off, this also "slightly flares" out the coupling sleeve.
Then next buff the "stubbed" section with a wire brush or mild flat file, till the end was clean.
Anti-Seize or like #90 weight gear lube both sections.
My bottom section was already connected to the tilt base. I then layed that section down, laying a long 2 x 4 under it. Next section on ground blocked with 2 x 4. line the section up and start the 2 legs only (section is slightly tilted away from base). Push it forward and raise the section up to line up the last (Top) sleeve. I have even gave that "peg" a "slap" with a recoiless hammer to pop it what ever direction it needs to line up.
Once I have all 3 legs lined up, pick the section up and start the "wobble" until the legs are pushed together and you can slip one of the bolts thru the hole. Nut it temporally.
...continue the wobble until you can do the same with another mounting hole.
Get the idea?
Then once you have it lined up this way, not uncommon to have all the holes NOT line up (again galvanizing reduces the openings) Then take a bit and run the other holes (5/16th's) Place those bolts/washers. etc.; in. Tighten those hand tight. Remove the other bolts ONE at a time. Ream and hand tighten each...Once all 6 bolts installed and hand tighten. wrench and ratchet them down.
Repeat each...then raise it up.
If your installing with tower standing up...ratchet straps and Hammer will most certainly be frustrating.
It can be done, I have done it by MYSELF with a ginpole and climbing belt, and a bucket full of extra bolts etc. tools etc.
It ain't fun!!! but doable
GL
All the Best
Gary