So I figured out an an entertaining new way to grind missions. Playing missions with other people is just about the least fun activity in GTA Online. Every single time at least one person has an armored Karuma and just runs straight into the objective and completes it. Utterly boring. I'm decent, but I wouldn't say I'm skilled enough to consistently complete the missions on hard without an armored car by myself, at least not at a rate useful for making money. So I decided to try something new.
I recently bought the Savage and have unlocked most (maybe all?) of the Merryweather options. So basically what I've been doing is trying to use air tactics and coordination with Merryweather + Lester to complete the missions. A few of them are difficult to complete with a chopper because they require you to NOT destroy a certain vehicle. But missions like "Hit 'em up" or "Cleaning out the cat house" or "Extradition" can be really entertaining. Generally I try to stick to the just the cannon on the Savage to give it a bit more of a challenge. "Death From Above" was particularly fun and challenging because the police just keep coming and you have to exit the helo to photograph the body. I ended up calling in the Merryweather support chopper to fend them off while I went to photograph the body. Then I hopped back in my chopper and called Lester to clear my wanted level. Playing like this is so much more satisfying than Karuma Grinding. Also, I feel like I'm putting my very expensive Savage to work, and it's great. It's a little heavy and slow to maneuver, but damn it packs a punch. Leveling out with the hotel in Sandy Shores and using the rudder control to rotate while simultaneously barraging the second floor with high explosive machine gun fire and watching the kill count repeatedly do +1's in "Hit 'em Up" was pretty awesome. They never saw it coming.