Yes, The is will work (if I am following you correctly). What you are describing, if you wish to sound professional, is called "blocking". If you install the way you described, you will be able to come back and gyp your ceiling in the garage. The gyp board will just attach to the blocking. If you nailed the blocking to the "underside" of the trusses, you would have to contend with the blocking since it would be in the same plane.