I agree with the warning about running on tracks barefoot. The first time I tried on my HS's freshly rebuilt track I did notice a lot more friction on the un calloused parts of my feet. Part of that is because the new track are still very rubbery and bouncy and rubber inherently has lots of friction. Plus what RunWest said, those little bits of rubber are great for kids in track cleats, harder on bare skin. That said I also went back several times and as I really focused on my stride, shortened it way down... made sure I was placing and lifting each foot as directly and with as little braking of pushoff s possible, that also alleviated the problem.
As for grass, just remember with grass that although it will give you a nice cool and natural sensation on your skin, all that soft squishy sod does the same things running shoes do, they lessen the pain of impact on your feet.
As Barefoot Kenbob always preaches, there is no surer, faster way to find the perfect gentle, zero friction, low impact barefoot stride than in actual bare feet on asphalt. You WILL feel your stride change. Imagine thos cartoons with Wile E Coyote and Roadrunner, when their bodies are bolt upright and motionless and there feet are just spinning in a perfect barrel sized circle under them... that is you running barefoot.