The most important reason to study Garcia is to develop an easy way of singing. His method is common sense and natural. There is no forcing or using silly tricks.
Garcia’s singing exercises, if practised with determination, provide everything that is needed for singing. His singing books are available free on the internet.
Here is a video of me singing “Una Voce Poco Fa”. I am self-accompanying so it is not as easy for me as singing with a accompanist or orchestra but you will hopefully see it is easy and fun for me to sing. It is simple: I breath quietly and pronounce with a tongue that is mostly returning to or against the lower teeth. I feel no tension at all in my throat. I could sing for hours like this.
I really recommend that singers who are struggling to give Garcia’s singing books a go.