There are only two specialist jobs in a gun crew. That is the Rammer and the Ventsman who also lays the gun. The other part of the crew can be infantryman and labourers. The rammer needs to be a strong man to weild the rammer and sponge. Both of these are essential to the safe firing of the gun. The ability to swop over the rammer is important in a long emgagement as ofter 20 or so rounds he will be feeling it considerably. Often forotten is the amount of ramming affects considerably the muzzle velocity of the gun and hence the range.
Only the gunner laying the gun needs to be educated in maths to estimate ranges if possible. This would be the corporal/bombardier in charge of the piece. The sergeant in charge of two pieces would likely be the most experienced gunner. Now this was normally by practice and experience. Only the Lieutenant would be cadet educated who would be incharge of half a battery. This is the same through all the armies. There were a few examples of NCOs being schooled trained but these commended a division (a pair of guns). In some countries this would be the role of the lieutenant and others by an NCO. Both having the same role. The latter was cheaper to pay than an officer.
Moving the guns is hard work but if you can find infantrymen to do this then that is much better.