I did a bunch of reading and video watching on bark tanning since o plan on doing this with my deer and squirrel hides from this year. From what I came across, you sure can without the grain. It just makes for a softer less water resistance leather. Though the oil you decide to use if the hide makes a difference too. Like tallows make a more firm leather and thinner oils like emulsified egg yoke is softer.
I havnt tried it yet, but this is what I came across.
Kyle