Hanging ceiling drywall, rafters not all 24” center?
I would suggest that you install 1x4 furring strips (example not a recommendation) across the joists.    Use the picture below as an example.   
Notes:

24&quot; is too far apart to install 5/8&quot; on a ceiling.   It would sag over time especially in a garage where there are more humidity and heat changes.   So even if they were dead on - still a bad install.   No inspector near me would OK this (yes I know its a garage and might not be inspected).
I use 1x4 furring strips on basements and garages for ceilings when I need to.   I have used 1x3s and what I have found is when you screw into the edge of them you can split the strips or crack them.   Furring strips are cheap wood - give yourself the extra inch.   The cost comparison is pretty negligible - might cost $10 more for the garage.
The wider furring strips allow for you to install hooks and things easier too once the drywall is up.
If there is a room above the furring strips will help you hold the insulation.  Make sure to make rigid boxes to separate lighting before drywalling - much easier to do this beforehand.
If your walls (drywall) isn't up yet make sure your furring strips near the wall are about 6 inches out - you do not want to screw the edges down.   This will allow for movement and the drywall on the walls should support this.
These furring strips since it is 5/8&quot; and a ceiling should either be 12&quot; or 18&quot; on center.   18&quot; is probably adequate for a garage.   You need at least three tie-in rows.
If you have a nail gun this is about 30 mins of prep for a garage.   You can use a chalk rope to snap your grid and you should only have 10 or so cuts.   This 30 mins of prep will make installing the drywall on the ceiling be twice as quick.

Side Note:  Concerning point #1 - I am not disagreeing about the ability to install the drywall on 24&quot; on center.   But I have done a lot of houses.  Most are 24&quot; on center, most/all old ones have cracked seams.   Most have no strapping or blocking.    So sure put the drywall up and watch all your seams crack over time.   And when your seams crack there isn't a long-term fix - yes you can always remud the seam and it will crack again.    The fact is you will hang stuff in garage, you will have insulation on top of the drywall, you will be hanging shelves, you will probably have a garage door opener.   Yes the garage does not have to be the Taj Majal but doing a tiny bit of prep is the right way.   You can certainly do a substandard install and say &quot;it's the garage&quot;.   The point of my answer is the furring strips are cheap and easy to install AND make the install much easier and last longer.   I have done this to any garage or basement that I have redone - (basements are a great example - if I do a basement without furring strips you can for sure see the bumps on the joists after a bit no matter how good of a job you do.  I am not saying anyone without inspecting it and staring at the ceiling would notice but hey I can see it.    If you use furring strips almost impossible to notice.)