Leolady, I can really understand the feelings you have...it can be scary thinking of how you will manage with 2.
I do feel that trying to resist a baby's (or even 2 babies!) normal, physiological need for frequent, unpredictable feeding can be harder work than just going with the flow...truly.
The pressure people feel, from different sources, not to respond (fears of 'spoiling', bad habits and the rest) is enormous, and it can be exhausting doing the things like leaving to cry, putting down and then picking up (baby must feel like a yoyo, and they can get genuinely distressed).
What are we teaching our babies when we say 'sorry, baby, you have to scream and scream and scream before anyone takes your needs seriously'....we would accept this is distressing for an older child, or an adult. Why would it not be distressing for a baby who has no other way to express himself, no words or behaviour....?
You can teach babies by leaving them to cry - some babies do learn in a few nights. But what have you taught them?