You can also use agricultural lime, like for your garden. Like Bob said, keep it stirred and keep checking because of differences in temp and strength of lime. Just keep pulling on hair each day in the thick areas of hide until it slips. You need to have a log and scraping tool ready when it slips. The grain is on the hair side and at the base of the hair. It will swell and look a little like cheese or a thick sponge and will be a little different color than the actual hide. You may think you are cutting into the hide at first.
I think for drums you want a thin hide so I would plan on taking the grain off of a thick moose hide. Try one of your sections at a time, removing the hair can be some work and a learning experience. Also, once the hair is off flip it over and scrape the flesh side again. You will be surprised how much tissue will be on there.
You can also mix a little white vinegar in water and put your scraped hide into it for a little while. Vinegar neutralizes the lime, but too much vinegar is not good either. Like Bob said, rinse it really well to get the lime out.
Good Luck