Well it doesn't take any training, just a brief explanation to tell them to pick up the wounded and keep low. It only takes a litter team one time bringing back a chest wound to hear he won't be loaded on an ambulance to not make that mistake again. As for young nion-musket carrying soldiers serving as ambulance corps, they don't have what it takes. Ambulance Corps is not a place for the physically weak. They need to be quite strong and in shape. Same was true with the original cast.
As for training them as dressing assistants, applying dressings and splints is the job of the Assistant Surgeon, not the litter bearers. They are simply brute force labor to move bodies and quickly and efficeintly as possible.
As for using musicians as ambulance corps... Certainly! And the Liberty Hall Fife and Drum served as litter bearers with the Confederate Second Brigade At High Tide event and did an excellent job!
Medical Director Bee's Brigade - 150th First Manassas
Medical Director Evans' Brigade - 150th Leesburg
Medical Director Valley District - 150th McDowell
Chief Surgeon of Division - 150th Seven Pines/Seven Days
Chief Surgeon of Division - 150th Sharpsburg
Chief Surgeon Heth's Division - 150th Gettysburg