It's usually easy enough to sync the carbs at idle just by putting your head down between them and listening to the relative volume / tone of the air, but nothing wrong with a gauge if that works for you.

Then work the throttle by hand while watching the pistons. Adjust the linkage so both lift off at the same instant.

Adjust the mixture at idle by *gradually* turning the jets on both carbs up or down one or two "flats" at a time. If there is no change in the idle speed or quality after a full turn (or if it gets worse), try going the other way. You'll find a point where the idle speed is the fastest. Turn down the idle speed screws as necessary (being careful to maintain sync) and continue adjusting the jets for fastest idle. It may very well be necessary to finish by adjusting each carb individually.

Recheck idle speed, sync at idle, and piston movement coming off idle.

If it runs like &%$# after that, you've got the wrong needles.