I also workout in my garage.
To echo what everyone else has said, hold plates. I only use 10lbs of weight. Right now, my shoulder circuit is this
-60 reps partial ROM shoulder press (I use a 5lb DB handle, but a plate would work just fine. I press until the point that my triceps are about to take over and then reverse the rep)
-10 front raises (10lb plate)
-10 lateral raises (10lb plate)
No rest between movements. And I do band pull aparts in between sets of EVERYTHING on my upperbody days.