Not too many ideas on the web for large shakers, but plenty for spray cans. This one seems like a good idea to me, and could be adapted and scaled for any size can. Whatever you do, make sure that you clamp the lid on well. It is reasonably quiet too. The vibrator type tend to be very noisy. This could be much smaller if made with direct drive using an old treadmill motor with speed control. You could experiment with canting the clamp by say 45 degrees and it may stir/mix better. If you have an old bowl washing machine, and the room to keep it, this shaker could possibly be built to hold the can horizontally, and canted inside the existing machine bowl.