There are no secrets in shooting. Ned Roberts, in his book the Muzzleloading Caplock Rifle, details how he was taught to shoot.
The U. S. Army marksmanship manual gives a comprehensive treatise on shooting. There are many more . All of them stress practice.
I can't say I was self taught, because most what I know about shooting came to me by reading, as I have not a mentor.
However the vagaries of shooting with black powder I learned mostly from my late friends Bruce Schwindt and Jim Fleming.