I still can't offer you any advice on nailer brands, but most of the bad roofs I've seen were done with a gun. Not due to the gun, but the rape and run mentallity of the roofers. 22 squares is a good size roof though, big enough that a nail gun might be worth your while in time savings. I've forgotten how many squares my dad's roof was, but it 20 trips to the dump with a 5 yard truck. It had 5 layers on part of it, and get ready... 7 layers on part of it! I swear I could hear the roof going aaah, when I tore it off. Not only was it big, it was very cut up. It's the worst roof I ever had to deal with.
As far as keeping your reveal running right, it's mostly attention to detail, which it sounds like you already have. I start by snapping a line for my first course, and gauging off that course with the gauge on the roofers hammer. Most people run the first course upside down, but it's better to cut the tabs off for the first course, so the course that goes on top of these will seal to the tar on the top side of the single. Most folks also go with a half lap back from the tab below, and that works ok. The roofer that taught me, used the gauge on the shingle, and cut back that far. Doing it that way, the slots in the tabs don't repeat for seven courses. If you're right handed, cut off the left side of the shingle, and work from left to right as you're looking at the roof. I'm left handed, so I roof backwards. So I'd usually start my courses by cutting all my starters for 7 courses, and haul the cut offs to the far end of the roof where they'd get used up as I finish the courses. Then I scatter groups of 7 shingles about a shingle length apart across the roof. Nail the 7 starters on, park my but at the starters, nail the last tab on the shingle already laid, but the next one to it, gauge off the one below at the 2nd slot, nail it there, nail the first tab, and nail the closest end, shift my butt slightly up the roof, grab the 2nd shingle off the bunch of 7, repeat ad nausium. When you reach the end, those left ends you cut off will butt factory cut to factory cut, and trim the waste off the overhang. If you're still running straight at the top of the seven courses, start another 7, if off, snap a new line, measuring off the bottom of the roof.
Use 2 nails at each slot if you're in a high wind area, and peel off the cellophane looking stuff off the back side too. Most areas, roofs stay on fine without doing that. Oh yeah, don't use red chalk for snapping lines, unlike blue, it doesn't wash away.
