Railfan, if you are passionate about this, you have GOT to get yourself a good basic education about steam. Hot Water and Rich and others are not here to offer a steam locomotive primer. They are not going to have the time or patience to answer every single question you have, because they've answered each question you have multiple times already on the Forum over the years, and you may frustrate them by asking similar questions over and over. And while their answers will be helpful to you, by the very nature of this Forum they will only be able to cover the very basics in them. If you really want to know about a topic, you're just going to have to study it. This Form represents a very tiny percentage of information available about steam.
Example: Hot Water answered your very basic question. He is, of course, able to write scores of pages on the subject, but do you think he wants to do that here? Do you think he has the time to write the definitive master class on steam locomotive firing?
You thanked him for his answer--that was very kind. However, Hot Water may sense in you a lack of interest, because you seemed to have been satisfied with the answer, and gone on your way--and perhaps you were. But...Did you really get everything you wanted to know out of his answer? Or did his answer make you think up other questions? Like...what's the BTU difference between coal and oil? What's the BTU difference between different coals, and different oils? What does he mean when he says there's a "very large flame" on an oil burner? What does "slow reacting" mean? How does the oil even get into the firebox? Does it just flow out in a stream like when you turn on a hose?
It's great that you asked the question, but I think follow-up questions based in the information given previously might make it seem like you have a deeper interest. Asking educated or intelligent questions of these folks might lead you to more understanding. Asking questions just for the sake of asking questions might not get you far with some folks.
Listen--do yourself the biggest favor you can: Buy this CD for 20 bucks and READ the answers to every single question you've ever had about steam locomotives. There will be some subjects here you just don't understand--but then you can come here and ask for clarification. This will enable you to ask intelligent questions that will lift you above the fray.