The double-top-secret trick (don't tell anybody about this...) is getting the tension on the sections between the crank sprocket and the forward cam, then between the forward cam and the rear cam. I use Binder Clamps, the ones you use to hold paper piles together before you punch and binder-book them. They are a little stiffer than the chip clamps, plus I have a bunch of them for lots of other things. The chip clamps tend to be busy clampng, um, chips bags. Plus since they are technically under the territorial supervision of mrs dr bob, they can serve no useful purpose in the garage.
Loop the belt around the crank sprocket, maybe with a rubber band to keep it in place. Then pull it tight towards the front cam and fit it over that sprocket while verifying that the marks line up. If there's an issue, rotate the cam with a wrench (17mm IIRC) a bit clockwise of the mark, then verify the mark with the belt on after pulling gently counterclockwise on the cam with that wrench. Fit a binder clamp to hold the belt on, or use a plastic cable tie to do the same thing. Go to the rear cam and do the same thing, rotating the cam slightly clockwise to fit the belt, then pull the wrench counterclockwise with the belt fitted. Verify that the timing marks line up while you have tension on the wrench, and add the binder clamp or cable tie. You cam use a mirror or maybe your camera phone to verify the rear cam marks lineup, since there's no easy way to get your head down there by the rear cam to eliminate parallax error with the belt installed.
More: There's really no such thing as "half a tooth off". Unless you've milled the cylinder heads or the block surfaces, half-a-tooth "errors" can be traced to the crank exactly not at TDC #1, or visual errors with alignment marks. That's where a small square and a mark on the belt (or on masking tape on the belt...), combined with the mirror or cell camera, will help you confirm the alignment before you "pull the pin". If there are still questions/doubts, remember to use a wrench on the rear cam to pull it snug counterclockwise to take any slack out of the drive section of the belt, then look at the marks again to confirm alignment before you pull the tensioner pin. All belt slack will be between the rear cam gear and the crankshaft, right where the tensioner and idler will be able to take it up.
At this point, erase your belt marks or lift that masking tape, remove the clamps or cable ties, cut the rubber band if you used one, and rotate the crankshaft clockwise two revolutions to TDC #1 again. The belt is tight via the tensioner at this point, and the marks should still line up. Use new marks on the belt or masking tape again if you need them. (The old marks won't help you at this point.) If OK, rotate the crank two more revolutions and verify lineup one more time just to be sure before you start putting more pieces back on.
Virtually all belt and cam timing errors can be avoided this way. You'll find it a lot easier to fall asleep at night after doing it this way, with no nagging mistimed worries clogging your head.
----
For the tech-heads:
There are two pistons at top of stroke at any 120º point from that TDC #1 mark on the crankshaft. With the crank rotated 60º (one sixth of one full rotation) from that mark in either direction, it's safe to spin the cams with no worries about valves contacting pistons. For folks who accidentally take the belt off with the cams 180º out (crankshaft at top of #1 exhaust stroke, 360º crankshaft from compression TDC #1) this may be a relatively safe way to recover without putting the belt back on, tensioning it, and rotating everything together to get everything lined up again. Turn the crankshaft that 60º counterclockwise from the #1 mark, turn the cams the 180º to align their marks, then bring the crankshaft clockwise to line up its mark again.
The very important warning about "only turn the crankshaft clockwise!" is critical while the belt is installed. Rotating the crank counterclockwise with the belt installed puts tension on the tensioner squeezing/collapsing it, and puts the slack belt section between the crank and the forward cam drive where it risks jumping teeth at the crankshaft as you turn it. Once the belt starts around a gear without seating in the cogs, the belt will be too short if you continue much, and either stretch/break the belt, damage the tensioner, or break the nose off a camshaft. None of those options sound appealing, to me anyway.