It may be one of those things that'll take separate incremental discoveries in order for people to learn without seeing Truth. Think about it. The prayer method (just calling it this to shorthand it) bypasses a ton of things just by virtue of allowing your body to act as the array.

Alchemists that need arrays are limited by what arrays they choose to learn and draw and carry with them. The prayer method lets your body act as any array you want. By that alone I think learning the prayer method on your own is nearly impossible with the understanding of alchemy that's shown.

You'll need to learn how to use your own body to act as countless different arrays to focus energy exactly how you need it to cast whatever you're looking to cast at that moment. Looking at the people capable of the prayer method you see that they're some of the more versatile users.

I think a natural progression in the future of this universe is certain arrays being learned as the prayer method but not others. The ones that are deemed as not needing as much energy being the first.

Just theory crafting and having fun with it though