Moose hides are large so I think you can work one quarter to see if your results give you what you want. I also suspect the quarters will vary in thickness from on each to the other, so for drums you want to try and cut from an equal thickness as much as possible. Not sure what you plan on using for the drum body, but that can be a challenge also if you plan on bending wood into a hoop. The quarter you choose will need the salt removed. Soaking it in many changes of water will work for that, but having a moving water source is good, such as the creek you mentioned. As Bob said, if you leave the hide in water long enough the hair will slip and it will not require neutraling the wood ash or agricultural lime after the hair is removed. When using ash or lime it changes the ph in the hide and makes it swell and can get a soft cheese like texture and the hair is easily scraped off. If you use that method you can also scrape the hair side epidermis layer off, which will make the hide thinner. This method is used for brain tanning hides. Again, if you use ash or lime you will need to bring the ph back to normal and you can use a vinegar and water solution to neutralize it. Your hide should be really clean now, having the hair and meat tissues cleaned off leaving you with raw hide. You can stretch it and let it dry, then sand it to thin and smooth it more or if you have your hoop ready you can put it onto the drum then. It is a process that sounds harder than it is so give it a try. Just make sure you check the hide often once it is in the water or lime to see when the hair slips. If you let it go too long the hide can actually fall apart or decompose. Good Luck!