You do not need battery acid
Wear rubber or latex gloves and use a plastic bin.
Use formic acid at 7.5fl oz in a solution of 7 galls warm water and 6lbs of good salt. This will fix the skin first.
Shave it down and then drain off after about 2 days
After this use any tann you like but Lutan FN is a tan used for taxidermy work.
7 galls of warm water, 2 caps of tanning oil, 3lbs of salt and 2oz bicarbonate of soda, and 12.5oz of Lutan FN Tanning powder. Mix in put the skin back in and punch it about with a stick, do not use anything made of iron or steel.
I use a plastic dustbin, to tan a skin the size of a fallow you will need to use about double, as the solution is gauged on 3lbs dry weight of skin.
After about 2 days take out and drain and peg out and when nearly dry rub in some warm tanning oil and then work the skin over a a pole or old spade head to break the fibres up and it will come out as white calf leather.
This is dressing a skin NOT tanning, tanning means hair off, dressing you keep the hair on.