We have always ground driven them in long lines. No blinders and no cart. They can bend and they can do everything that you do under saddle.
We always run our lines through a ring attached near the back of their saddle. It gives them a lot more incentive to bend through their whole body and not just their necks.
They quickly learn that they stay straight when pulling and bend when riding.
When they won't stand still, we drive them to a rope with a snap on it and snap them up to a halter we leave under their bridle. We stand behind them, move around, flop the long lines, drag them all over their rumps and legs and just keep them tied until they stand still and rest a hind leg.