I took the first stealth cert on my flash and have been riding around on flashes dropping tank mines on sunderers and other vehicles. I pick up the flash at a base near a base that's under attack, and use the flash to ride in behind the enemy. Riding up behind a prowler shelling a base, dropping two mines, then riding off with him exploding behind me is great.
I picked up 40 certs in an hour doing this just now. Not super amazing, but it's extremely fun. The downside is I use up infantry resources really quick, 150 per kill. Quickly went from sitting on max infantry resources and 40 mines to having 20 mines and 0 resources.
The best life I had was when I rode my flash directly into a base, hopped off and dropped two mines on a sunderer, then hopped back on the flash and actually managed to ride away with at least 30 people and numerous prowlers hanging about. I drove the flash to one of the little mini bases, repaired it, swapped to medic to heal myself, swapped back to engineer, then went back in and blew up a second sunderer that had moved into the exact same spot. I didn't get away the second time, they shot me right after I dropped the mines. I did blow up the guy that shot me in the ensuing explosion, though. Just those two must have given me 10 certs with all the bystanders and bonus xp (we were defending the facility, so that was providing a bonus).
I'm surprised at the number of sunderers who don't use mine guard. I only have two mines, so if they had mine guard it wouldn't kill them. It's also a bit surprising how few tanks react to the flash riding up behind them. A few ride away when they hear the flash, but most of them just sit there and don't even turn their turret around to look.