So, your best conditions are to walk a creek looking for a "typically" Red or Yellow sandstone boulder, with a flat surface, that you can roll into the edge of the small or large creek. Sit with your legs in the water and slant the stone slightly away from your body. Use your hand to splash water onto the surface of the of the sandstone and start grinding away from your body using both hands. You will quickly start forming a nice "dish" into the sandstone. This dish will hold the slurry and make the grinding more efficient, by having more of the surface of the Ax in contact with the abrasive surface on each stroke. Wash this dish out often enough that you always hear the nice grinding sound. If you don't wash the stone as needed the ground aggregate will glaze the sandstone and make it less efficient. This is why it is nice to sit in the creek and do this work, you can easily "splash" clean the grinding stone, without getting up and carrying water every few minutes. Also, this type of manufacturing is best done in July or August, when you "want" to be in the nice cool stream for hours at a time !!
As for polishing, this is best done with charred wood. Charred wood concentrates the molecular sized "silica" that is transferred from the ground into all organics. (wood & weeds) That fine silica will give the best fine polish to a Celt. Char a hardwood log deeply, sit on the log with it slopping down hill, and polish the celt the same fashion you did the grinding. You do not need water to polish!!