It has been hit and miss for me. Some days I hit a base loaded with GR, or several, other days not. Some days I still get wreaked with a base that has no GR. I would just keep attacking. I'm always prepared for GR with air, as much as you can be prepared, and let it rip. Pushing through works better for more than 2 GR, but if less than 2 GR and close barracks and factories and I just attack all in and push through. With baiting, it seems the troops take too much fire on their own and the GR responds quickly back to my attack.
I have 3 bases: 6, 9, and 10 and I usually complete 3-6 attacks a day per base.