sand it, or run it through a well tuned planer and wet it, alcohol won't raise the grain but water will work too. My VERY limited experience with walnut is that all the figure is in the crotch areas, the larger the limb and the more perpendicular it is to the trunk, the more figure. the exception would be fiddleback, but I think the best figure in the log would be in the stump. if you're planning on checkering the stocks, see how porous the wood is, I understand some black walnut can be very porous, and that can ruin checkering. good luck, I hope you find something good in your log.
Tim
