Quikrete is fine to use. My hole is about 18" across on the top, and "bells" out on the bottom, 4ft down. There's a slight "cut" on one side, to help keep it from being a cylinder, and possibly spinning in the hole from huge winds. Yeah, that can happen, I've heard of it from others.
Once you dig the hole and flatten the bottom a bit, pour in 1 bag of GRAVEL (for water drainage, to help keep pole from lifting later). Then, place a flat patio PAVER on the top middle of the gravel. Your pole bottom sits on that, It'll keep the pole from sinking into the ground. Then use some stakes and 2x4's to completely, 100% PERFECTLY level the top of the pole in the hole, East-West and North-South. Get it PERFECT. Oh, by the way, you should also have drilled a hole through the pole about 1 foot or so UP, and place a bolt (or "all-thread") through it, that's long enough to hang out both sides of the pole. Nut it down. Yet another thing to keep the pole itself from possibly spinning inside of the cement after huge winds.
Then mix and start slowly shoveling in the mixed cement, a little at a time, alternating around the hole so as not to "push" the pole to one side. After you get a foot or so of cement in the hole, RECHECK the level on all sides! IF it's changed a bit, adjust it before it's not possible anymore. YES, at that point you could still man-handle the pole a little bit if needed.
Once you have all the cement in the hole, it should be enough to have a slight "dome" top above ground. That keeps rain water that runs off the pole, from pooling right there and causing issues.
Double-check your level again, before the cement completely sets up too much to do anything about it.
I cover the wet cement with some of the left over cement paper bags, and keep them slightly damp while it all hardens over the next 5-7 days MINIMUM, before putting the polar mount and dish on the pole.
Don't RUSH this, because IF you don't get this right, it creates a real mess later. You can wait a week, believe it or not.